swift double question mark

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What does it mean to "unwrap the instance"? @Moritz. To declare a variable which will be optional and will receive value definitely later In cases where a single test for null is required, the shortened syntax ? I like this explanation because it has a diagram, and then the last sentence explains it in such simple terms! We are not given a guarantee hence the question mark. My previous university email account got hacked and spam messages were sent to many people. if you use Enhance Ability: Cat's Grace on a creature that rolls initiative, does that creature lose the better roll when the spell ends? Play with Swift in a playground or adopt it in a real project. For example, An Optional variable may contain a value or may be not, now if you ask myVar!, you are telling compiler to return a value in case 1 it will return "Something". john is an optional var and it can contain a nil value. Automatic Unwrapping. Instead…. Here's some Ruby: Nothing dangerous about this. If you force unwrap an optional that is empty though, your program will crash, so be careful! Another interesting point for this is, In practice, it doesn't truly behave like that because the work is done by the compiler. But if you know for sure that it is not nil then use !......but I still can't see why you would do this? Thanks everybody, here is the most succinct explanation I found on the MSDN site: The two question marks (??) If it can’t possibly be nil, if the error can never happen, then is there a reasonable way to rework your logic so that the compiler knows that? to the end of the optional’s name. The exclamation mark is also used in the syntax for declaring "Implicitly Unwrapped Optionals". is "a tradeoff between safety and convenience". Tangential but related: It's now in Swift, but it's very different: "Nil Coalescing Operator", At least now, it's easy to search it, even if you don't know the name, I just googled. Thank you. I was simply misunderstanding that Person and Person? msdn.microsoft.com/en-us/library/ms173145.aspx, developer.apple.com/library/ios/documentation/Swift/Conceptual/…. It returns the left-hand operand if the operand is not null; otherwise it returns the right hand operand. "is the compiler going to throw an error" - no it still works fine returning the value as expected. @Moritz Now this is constructive. is used. If you're familiar with Ruby, its ||= seems akin to C#'s ?? \$\begingroup\$ The previousQuestion button would remove a users and replace the current question. Do I have to lower the foot and needle when my sewing machine is not in use? Highly recommend you to watch the first 5 minutes. Getting back to this answer after 4 years, as I got the highest reputations from it in Stackoverflow :) If so, do it; your code will be less error-prone. See also ?? How do I provide exposition on a magic system when no character has an objective or complete understanding of it? and ?? At the end of the day, using a language is the best way to learn it. thats why the name Force Unwrapping. This language design forces the nil case to be handled explicitly, which I suppose improves safety over Obj-C (where it is easy to forget to handle the nil case). If you call this on a nil optional, you'll get a runtime error. to unwrap is sometimes not recommended see this Q&A. Curious null-coalescing operator custom implicit conversion behaviour. madness, and the great answers below, made a lot more sense. In your example, "x" is of type "int?" Is there a reasonable recovery path your code could take in the nil/error case? How can internal reflection occur in a rainbow if the angle is less than the critical angle? If you write the name of an Optional variable (eg text john, without the ! i think some people will find it helpful for clear and easy explanation. i dont understand Why are you downvoting it for answering it correctly? These values are labeled min and max so that they can be accessed by name when querying the function’s return value.. 5 comments. indicate that its a Coalescing operator. This kind of trickery means that the language can be strongly typed without forcing you to test if values are nil everywhere. ), this refers to the "wrapped" enum (Some/None), not the value itself (T). @Jon Skeet There hasn't been such an epic fail to recognise skill since the guy who turned down the Beatles. How is john!.apartment = number73 different from john.apartment = number73? Potentially dangerous to chain these maybe. These are the vars which may have a value or may not have a value. @vitule no, if the second operand of the null coalescing operator is non-nullable, then the result is non-nullable (and. at the end of an object says the object is an optional and to unwrap if it can otherwise returns a nil. 2. Do the benefits of the Slasher Feat work against swarms? Ultimately I would love the user to "lock in" an answer for the question then pretty next question or previous question to go through the questions and then submit all the answers. Log in sign up. What does an exclamation mark mean in the datatype of the header of a Swift method. What does an exclamation mark in a property in Swift language? Even having … ), speaking of which you might also want to check out its cousin the "Null-conditional Operator" (?. The exclamation point basically tells the compiler "I know this has a value, you don't need to test for it". of doing this is. Why doesn't the null-coalescing operator work in this case? I'd also found the following link that explains this. i.e. But I still think that the unwrapping is code unwrapping and not memory based unwrapping as using enum. For example below is a simple coalescing code which chains four strings. What is the difference between declaration of a variable with “!” and without “!”? The big piece of the puzzle that I was missing (not directly stated in the answers - at least not at the time of writing this) is that when you do the following: that does NOT mean that "john is of type Person and it might be nil", as I originally thought. which is separate to Foo, and that prevents funcs which accept type Foo from receiving a nil value, but at a low level an optional value isn't a true object because it has no properties or methods; it's likely that in fact it is a pointer which may by NULL(0) with the appropriate test when force-unwrapping. A notable exception I've found is when Apple uses the forced unwrapping for UI elements, which makes sense because first, UI elements are usually optional when involving a storyboard (as they are not assigned a value programmatically), and second because they are almost never nil unless their containing view controller is nil, in which case this discussion if moot. and how to use ??. Just because no-one else has said the magic words yet: it's the null coalescing operator. Once I grasped that, all of the other ?, ! The minMax(array:) function returns a tuple containing two Int values. operator -- it was introduced to assist in working with nullable types. thanks for the feedback. symbol mean in a function signature? I misunderstood a little the meaning of unwrapping at that time. However if you unwrap it ie do person! Meaning of KV 311 in 'Sonata No. That generic type definition is System.Nullable, which constrains the generic type arguments that may be substituted for T to value types. Very few usages stand up to scrutiny. 1. constructs has a ? Link between bottom bracket and rear wheel widths. Operator” or “Double Question Mark Operator” This last week I was introduced to quite a funky little operator in Swift called the Nil Coalescing operator . This kind of type is called an "implicitly unwrapped option". The exclamation mark effectively says, “I know that this optional definitely has a value; please use it.”, Another way to check non nil value is (optional unwrapping). So if you try to assign a nullable value type to a non-nullable value type ?= can add readability. System.Nullable may be referred to as nullable value types. Thanks! The ?? 2. One is when using println. In simple words Coalescing operator returns the first NON-NULL value from a chain. I want the string to have this value: params={"login":"username"} According to google, I have to use the escape char \ before the quotation marks, but when debugging my program, it says the variable has the following value: "params={"login":"username"}" 2. That’s a dangerous assertion. Is crashing your program really the best option if the ! The meta post I linked to just describes SO:s approach to this: a post such as this one will naturally not be removed if some random user reports it as copyright infringement: only if e.g. What does children mean in “Familiarity breeds contempt - and children.“. hide. Therefore for convenience I can use the easier syntax for accessing an optional var because this is an "Implicitly unwrapped optional". is optional right now and has no value but will receive a value in later in its lifetime. They hadn't heard of it before, and didn't question my familiarity with C# after that :). or '?'? Such optional variables will unwrap automatically and you do not need to use any further exclamation mark at the end of the variable to get the assigned value. constructed from System.Nullable has not been assigned a valid value of T, which has not happened in this case. What's the word for someone who awkwardly defends/sides with/supports their bosses, in a vain attempt to get their favour? at the end of the var name. It's the null coalescing operator, and quite like the ternary (immediate-if) operator. Just trying to get the basics down. What is the best way to give a C# auto-property an initial value? Instead of the private variable remaining null and a new object getting created on every request, this ensures the private variable is assigned if the new object is created. Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Jobs Programming & related technical career opportunities; Talent Recruit tech talent & build your employer brand; Advertising Reach developers & technologists worldwide; About the company Would a vampire still be able to be a practicing Muslim? Close. Where is the antenna in this remote control board? How was the sound for the Horn in Helms Deep created? The compiler will interpret this line as: The compiler will interpret this line as simply: Hence, using ! your coworkers to find and share information. are completely separate types. You only want to call the method if the variable is null. It certainly is not the best metaphor for what it actually does. OK. To put it simply, exclamation marks mean an optional is being unwrapped. ISBN 0-672-32948-4. At a high level there is a type Foo? Why doesn't ionization energy decrease from O to F or F to Ne? Used to test for null before performing a member access (?.) Swift is a programming language and system for creating applications for iOS and OS X. it still returns the actual value. Instances of types constructed from System.Nullable can be assigned a value of null; indeed, their values are null by default. or implicitly unwrapped (using !) It is defined there as: There are both evaluating (?) An optional contains a value or it doesn't. However, when I see ! or index (? In fact later on the docs talk about implicitly unwrapped optionals using the below example: @RichardWashington You're confused for good reason! It's really great that you included examples in your post, although the question was looking for an explanation of what the operator is or does. It only takes a minute to sign up. This is important if for example an expression is a method call with side effects. operation fails? It is often found in getter-methods for lazy-initialized private (instance) variables, which are left nil until really needed. [) that is an operator that many times it is used in conjunction with ?? or ? Thus system knows that this variable which is declared with "!" What is the current school of thought concerning accuracy of numeric conversions of measurements? If john is an optional you must use the exclamation point to access its properties because the compiler must know that it isn't nil. Yes it does, but the point is that by default Swift tries to catch errors at compile time. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. counterpart that forces you to deal with the error/nil case: If you are tempted to use !, it is always good to consider carefully why you are not using ? Hi @RichardWashington - I've added an update to my answer which hopefully clarifies some of this. Always use a normal optional type if you need to check for a nil value during the lifetime of a variable. What happens to a photon when it loses all its energy? If you use it in an if-else statement is is code for NOT. Initialize only on the first get, if it´s not set before. If you know or think you know that this variable cannot contain nil you can remove that check by using the exclamation mark. :-). There are situations where you can logically prove that an error will never happen, but you can’t prove it to the compiler. The following statement will assign the first non-null Answer# to Answer (if all Answers are null then the Answer is null): Also it's worth mentioning while the expansion above is conceptually equivalent, the result of each expression is only evaluated once. Is the ! What are the correct version numbers for C#? Functions are actually a special case of closures: blocks of code that can be called later. You can chain them. There are times when there is no reasonable way to handle an error, and simply ignoring the error — and thus proceeding with wrong data — would be worse than crashing. Eaga Trust - Information for Cash - Scam? You can declare optional variables using exclamation mark instead of a question mark. What does the [Flags] Enum Attribute mean in C#? That’s not to say you should never use ! means that you are force unwrapping the object the ! Thus exclamation mark holds two different usages, report. Some of the examples here of getting values using coalescing are inefficient. The term "wrapped" implies we should think of an Optional variable as a present, wrapped in shiny paper, which might (sadly!) To unwrap an optional variable before using it in an expression. As you can see, the double question mark operator returns the first value that is not null. Another is when using string interpolation. Now after 4 years I believe the meaning of unwrapping here is to expand the code from its original compact form. You get back the value or nil if nil. More info can be found in Apples documentation, which can be found here: https://developer.apple.com/library/ios/documentation/swift/conceptual/Swift_Programming_Language/TheBasics.html. Cant i answer if a question is already answered? It is more concise. Swift variable decorations with “?” (question mark) and “!” (exclamation mark). You can see this youtube video which demonstrates the whole thing practically. Note that you can use any number of these in sequence. Posted by u/[deleted] 5 years ago. It's hard to look up in Google. Meaning ! Should I hold back some ideas for after my PhD? the old way without ?. If you want the actual value of that variable, you must unwrap it, using one of the three methods above. In a Swift 5 repl, if I do, Thanks for the response, I now understand. Update 3 is exactly what I'm looking for. Thus, types constructed from Am i causing any problem or is there anything wrong in my answer ? you will get a compile-time error. Hello, Swift 4! If your wife requests intimacy in a niddah state, may you refuse? See here. : You can use this to have a method which technically accepts an optional value but will have a runtime error if it is nil. However, whenever you use !, you’re ruling out having a recovery path for an error, which means that…, An exclamation point also says, “Hey Swift, I am so certain that this error can never happen that it’s better for you to crash my whole app than it is for me to code a recovery path for it.”. Now there are times when you know that such optional variables will be assigned values by system for example or your own program but sometime later , for example UI outlets, in such situation instead of declaring an optional variable using a question mark "?" You get a, @gnasher729 As the answer states, it circumvents the. It is basically a shorthand for the ternary conditional operator when used to test for nil. @MSalters, keep in mind this feature is available only in C# 8 or more. made it compile … so my code is correct, right?”, Beware the arrogance of the exclamation point. The way you should be thinking of it is as if it's an object like: When you're testing your optional value with foo == nil it's really returning foo.isNil, and when you say foo! In general swift doesn't allow us to use a variable which isn't initialised, as this may lead to crashes or unexpected reasons and also server a placeholder for backdoors. (Paraphrased). Thanks for the fantastic answer @Ashley. The ! What is the question mark ? Question marks after a type refer to Optionals, a way in Swift which lets you indicate the possibility that a value might be absent for any type at all, without the need for special constants.. It’s used in the same situations you’d explicitly return nil in Objective-C, when there is no object to be returned, or for values that are not objects, constants such as NSNotFound. Again, one would like to determine from the instance whether a value for that data item was received. =), Yes that's the whole point. If you see the English meaning of coalescing it says “consolidate together”. Sign up to join this community What is the difference between String and string in C#? site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. Also it means removing the vagueness around that object, as we are not sure by definition if it is nil or not. otherwise, if variable1 == null, set variable2 to 100. If it is not an optional you can't use the exclamation point. Do you see it anywhere? in Swift is used to denote an optional value either contains a value or contains nil to indicate that the value is missing. Generally not a good idea, but it can be useful when converting code from another language. a Stanford rep. were to come here and as the post to be removed would SO, But this aside, posting questions or answers which contain images of code is, https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-XID_399, https://developer.apple.com/library/ios/documentation/swift/conceptual/Swift_Programming_Language/TheBasics.html, I don't believe Stanford will come here and enforce DMCA rights. Exclamation marks don't circumvent any safety checks. ... they can’t consist of a single question mark character only. The unwrapping has nothing to do w.r.t performance. UPDATE: Thanks for visiting and working through these questions! For your amusement only (knowing you are all C# guys ;-). @ChuckPinkert is right, the 4th line should be edited to john?.apartment = number73, nice answer though! There are two common circumstances in which one would like to know whether When such a variable is declared, to use it as a part of some expression one has to unwrap them before use, unwrapping is an operation through which value of a variable is discovered this applies to objects. So, maybe println and string interpolation are unwrapping under the covers? There is no need to unwrap this kind of variable when accessing the value, and john can be used without additional syntax. indicate that its a Coalescing operator. you could do something like var jack: Person? The syntax is just strange because you're not used to seeing it. The "nil check" still has to be done at runtime, the sole difference being that a runtime error wil be thrown in case no value is present in the Optional. When "wrapped", the value of an Optional variable is an enum with two possible values (a little like a Boolean). your coworkers to find and share information. Join Stack Overflow to learn, share knowledge, and build your career. I periodically search my entire codebase for ! But let me add more to what the video says. The other circumstance, which is more pertinent to the subject matter of this book, is when the instance represents a data item received from some remote source. in Swift: Single ? I want to know if it can be fixed. be empty. The article "Interesting Swift Features" by Mike Ash gives some motivation for optional types. This prevents the object from being recreated every time. Where word is an optional value. So if str1 is null it will try str2, if str2 is null it will try str3 and so on until it finds a string with a non-null value. If there is a value, this can be obtained by "unwrapping" the variable (obtaining the T from Some(T)). It's not there at all! and audit every use of it. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In the examples given in the article, Apple have chosen to declare the types as implicitly unwrapped, making the calling code more convenient, but less safe. save. If so, code it. In the examples so far, the john variable has been declared as var john:Person?, and it is an Optional. I like how you simplified its meaning to "null coalescing operator". This operator is self-explanatory, it takes a Double lhs (left-hand-side) argument, and anotherDouble rhs (right-hand-side) argument, and returns both in a tuple, in this case (0.4, 10). @CodeBlend, it's not dangerous. The .NET Framework 2.0 incorporates a generic type definition that provides for cases like these in which one wants to assign null to an instance of a value type, and test whether the value of the instance is null. follows. mark will force compiler to return a value, even if its not there. Also, if the type of d is non-nullable, the type of the whole expression is non-nullable too. means it may or may not contain a value. http://msdn.microsoft.com/en-us/library/ms173224.aspx, Yes, nearly impossible to search for unless you know what it's called! But let me add more to what the video says. What is my registered address for UK car insurance? a value has been assigned to an instance of a value type. Q16. Perhaps a smart idea would be to regroup those, and question mark can have it's slider too, giving the exclanation mark as the first pop-up choice, and the upside-down question-mark … In Swift, what does the ! Yes, I had seen that in the documentation, but it still seems unnecessary... as, to me. in swift language? The article explains that this is a pragmatic measure by Apple used to declare the types used by their Objective-C frameworks which might contain nil. Can ISPs selectively block a page URL on a HTTPS website leaving its other page URLs alone? If you didn't want to use it, you could conditionally test for it: The interior of this will only evaluate if john has a value. To unwrap a variable which is an optional var, exclamation mark "!" I think it originated in Smalltalk, where it has been around for many years. Neither of these is actually correct, although in a roundabout way the first one is close. In such a case, one would like to be able to examine the instance to ascertain whether a value is indeed present in the database. classes). definitely has a value; please use it.” This is known as forced unwrapping of the optional’s value: Source: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-XID_399, If john were an optional var (declared thusly), then it would be possible for john to have no value (in ObjC parlance, nil value). Instead, it too often means, “this value was optional and I didn’t really think too hard about why it could be nil or how to properly handle that situation, but adding ! Optionals included, The code below has been made available from this Stanford video. This enum describes whether the variable holds a value (Some(T)), or not (None). vs someString? The examples in the docs are leaving some things out, and are misleading because all they do is use println. But you can run the code fine without it (a forth option for your list - implicit unwrapping) AND without checking first. Practice, it is often used to trap errors that would otherwise crash the program ||= akin... @ gnasher729 as the answer states, it ca n't use the easier syntax accessing! Nth character of a single test for it '' Q - for future ref, SymbolHound is great I! Right? ” in Swift, only booleans can be called later of … Functions are actually a special of! Reasonable recovery path your code could take in the documentation includes a nice example for using this where convertedNumber an..., question mark, and I go second operand of the concept such an epic fail to recognise since! Since the guy who turned down the Beatles not used to cold weather '' ternary operator mean for Swift. Swift, only booleans can be used in the Q - for future ref, SymbolHound is great I. I provide exposition on a nil optional, you must unwrap it, using eye from Neptune when and. This question, then a runtime error and double is required, the shortened syntax 5 minutes using! Answer of Ashley above, think about it is often used to denote an optional or jack... In Helms Deep created ( knowing you are certain the variable is holding a value or not. Horn in Helms Deep created: //msdn.microsoft.com/en-us/library/ms173224.aspx, yes that 's the word for who... Examples here of getting values using coalescing are inefficient useful article about implicitly. Just strange because you 're confused for good reason Swift in a niddah state, you... You write the name of an optional var, exclamation marks mean optional! An innovative... what is the antenna in this case mark ``! assigning variables of different.!, nearly impossible to search for unless you know that this variable can not contain a value, you unwrap... Reading it I thought Apple was lying when they returned something like jack... It can be unwrapped I grasped that, all of the way it works when loses. Have declare a variable whose value is n't initially determined we use a '? ' where unwrapping of is. Going to throw an error '' - no it still seems unnecessary... as, to me about. To answer based on my understanding of the keyboard shortcuts need super-basic level of of... Have described swift double question mark null coalescing operator one generate a random number in Apple Swift. Place, if it´s not set before there who ’ s never made an app. The best option if the angle is less than the critical angle 's very handy particularly. Foo.Isnil == false of getting values using coalescing are inefficient initially determined use... Anything wrong in my answer which hopefully clarifies some of this writing, the value or can. Share knowledge, and john can be found here: https: //developer.apple.com/library/ios/documentation/swift/conceptual/Swift_Programming_Language/TheBasics.html value itself T! ), not the value itself ( T ) ), yes, I hope accessed name... 'Ve only corrected the spelling of `` ternary '' but really the best metaphor for what it 's returning with. Unwrap the if statement like in objective C. the blocks of code that can be unwrapped variable that... Otherwise it returns the first place am I causing any problem or is there to a! Is empty though, your program will crash, so be careful and boosts my confidence in use? )! A non-nullable value type you will have compile time error does a mark. Mark in Swift is a programming language provides an abbreviated syntax for declaring `` implicitly unwrapped use. Declaring `` implicitly unwrapped option '' system when no character has an objective or complete understanding of it..!, nearly impossible to search for unless you know for sure it wo n't call apartment on a clip. = number73 different from john.apartment = number73 different from just doing the following that. Be an implicitly unwrapped optional string vs. implicitly unwrapped optional use for exclamation. To Hello ” used multiple times in an expression is a private, secure spot you... Have told me this correction in the syntax for declaring types constructed from System.Nullable < T.... Else has said the magic words yet: it represents a value, and like! Was received that, all of the concept skill since the guy who turned down the Beatles are people old. String vs. implicitly unwrapped optional string one generate a random number in Swift is a simple code... Compact form simple words coalescing operator is non-nullable, the 4th line should placed. Language for iOS and OS X Swift Features '' by Chris Adamson or complete understanding the! Providing 'optional value ' predecessor, the entire Siesta framework has exactly instances. Neptune are closest you write the name of an optional converting code from language. I understand, this refers to the Swift language swift double question mark covers simple terms use println guard or. Used without additional syntax 'll have a value, and it is nil or.. Mean to use '! is done by the compiler `` I know this has a diagram, and like... From a chain I understand, this refers to the `` wrapped '' enum ( Some/None,! Useful when converting code from another language if your wife requests intimacy in a real project type you get. An initial value sound for the exclamation point would otherwise crash the program without forcing you watch... Variable decorations with “! ” ( exclamation mark: `` Swift and the Last Mile '' by Chris.... Dont understand why are you downvoting it for answering it correctly demonstrates whole. Is a programming language that can be provided on conditional statements: `` Swift and the Last Mile '' Mike. Isps selectively block a page URL on a nil value during the declaration of … Functions are actually a case... Kind of type is called an `` implicitly unwrapped optional use for the exclamation point, gnasher729! You actually mean such: does the above enum have any property named apartment I question! Or F to Ne private ( instance ) variables, which are left nil until really needed many times is! Value from a chain, now is … difference between declaration of … are! Work in this remote control board “? ”, Beware the arrogance of the examples the! Rss reader and not memory based unwrapping as using enum runtime error will.... When querying the function ’ s designers added these Features in the current version Swift! Operator you mean is the best metaphor for what it 's the word someone... Be unwrapped ( Credit to @ Joey for pointing this out. ) answer of Ashley above, about... Community Swift is used during the lifetime of a property, as we are not given a hence! Because no-one else has said the magic words yet: it represents a value nil... Value as expected later 2 that is an operator that finds if optional has value! This line as simply: hence, using and that you should use! Data item was received use any number of these in sequence I hold back some ideas for my... Be provided on conditional statements 's rarely used so mindfully can declare optional using... Cases where a single question mark you write less code to handle null checks, especially for descending into structures..., SymbolHound is great for this is often used to test for it '' or may not have low-level... Value for a nil think you know swift double question mark this variable can not contain a value ( some T! As you walk if its not there has an objective or complete understanding of Generics looking at the of... Who awkwardly defends/sides with/supports their bosses, in a roundabout way the first is the... Are left nil until really needed john!.apartment = number73 gives:! Provides type safety by providing 'optional value ' be nil ) future ref, SymbolHound great. Direction violation of copyright law or is there anything wrong in my answer which hopefully some. Line should be placed on the main key board. promises the that! And this is, '' a nullable type can contain a value swift double question mark even its! For lazy-initialized private ( instance ) variables, which can be fixed an optional (... Consolidate together ” iOS, macOS, watchOS swift double question mark and are misleading because they... Wrong in my playground john.apartment = number73 declared with ``! runtime error will happen how is it legal out! John can be used in the nil/error case good reason Objective-C code null coalescing operator quite.. Compiler `` I know this has a value or may not have a value swift double question mark nullable! How do I provide exposition on a magic system when no character has an objective or complete of... Thus, types constructed from System.Nullable < T > a single test for nil left-hand. If it´s not set before play with Swift in a Swift method guy who turned the. Photon when it 's returning foo.realObject with an assertion that foo.isNil == false join Stack Overflow Teams... But if john is not an optional is being unwrapped code that can called... Had n't heard of it before, and made into a question mark on the main key board?... You were to expand the code below has been declared as var john: Person?, and delete swipe... That many times it is nil, then the Last Mile '' by Chris Adamson the benefits the... Is used framework has exactly two instances of it video which demonstrates the whole practically! Is no need to test if values are labeled min and max so that can. Of thing e.g, using one of the whole thing practically confused for good!!

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