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Extension may not contain stored property but why is static allowed
(1 answer)
Closed 5 years ago.
Quoting the Swift Programming Language Guide :
Extensions can add new computed properties, but they cannot add stored properties, or add property observers to existing properties.
Why is that ? What's the technical or logical reason behind this ?
In simple words
Because properties need storage, adding properties would change the memory structure of the class
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Difference between static function and singleton class in swift [closed]
(3 answers)
Closed 6 years ago.
I have made a class that will contain all the utility methods. So, instead of making it as a singleton, I have marked the methods as static and accessing those methods by the ClassName.methodName without the need for instantiation.
Is this approach OK?
Just consider that a singleton is used in order to ensure that only one instance exists for a given class, and that there’s a global access point to that instance.
I believe that having all utility functions marked as static within a class is a good approach since, as you have stated, you will need to use ClassName.methodName in order to use them.
In addition, based on what you want to achieve and the information provided by this link, I would reassert that having a class with static methods is the best alternative.
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What is a good example to differentiate between fileprivate and private in Swift3
(10 answers)
Closed 6 years ago.
I'm starting in swift and opening a project created using swift2 from xcode 8 beta, the private modifier were changed to fileprivate. what does this keyword means? and how is different from private ?
fileprivate is one of the new Swift 3 access modifiers that replaces private in its meaning. fileprivate defines an entity (class, extension, property, ...) as private to everybody outside the source file it is declared in, but accessible to all entities in that source file.
private restricts the entity in the direct enclosing scope.
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Cannot assign property in method of struct
(2 answers)
Closed 7 years ago.
I'm studying swift and I'm trying to understand the difference between classes and struct, which as I understand it, is in these two points:
1) Classes are reference types, Whereas structures are value types. That means That When you pass an instance of a structure to a function, return an instance from a function, or assign the value of a variable That Refers to a structure to another variable, the instance is copied. In other words, structures exhibit pass-by-value behavior. Swift strings, arrays, and dictionaries are all Implemented as structures.
By contrast, class instances are passed by reference-no copy is taken.
2) Classes can be subclassed to add behavior; structures can not.
why these two errors?
depends on the structure ?, because a class does not give me the same error.
The reason you're getting those errors is that by default, the properties of a value type (i.e. a struct) cannot be modified from within its instance methods (e.g. your newRad() and plusOne() methods).
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Closed 8 years ago.
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Is there any situation when I need to declare the class data members as public?
Are there any chances of errors with such declarations?
Need to? No.
Any data access can be done through getters and setters:
(the truth of the above statement may depend on the language)
private member
public getMember()
return member
public setMember(newValue)
member = newValue
Instead of
public member
Errors? No. Well, apart from having to change your code to use the getters and setters instead.
Want to? Possibly.
The main disadvantage of using getters and setters is how pretty your code looks - how readable it is and code bloating.
See this for advantages of using getters and setters.
If using getters and setters classifies as similar to making the member public for you, then there are many scenario's where you need this at one of these kinds of access. Consider an artificial example of having a Car class. There would be many reasons why you'd want to get the windscreen member variable.
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Closed 11 years ago.
Possible Duplicate:
dynamic properties in objective c
How can I add properties to an object at runtime?
Is there a way to actually create properties in runtime dynamically in iOS?
I am experimenting something here, and just wanted to see if it be possible?
Thanks.
Properties are mapped to methods so you can add properties dynamically the same way you add methods dynamically using -[NSObject forwardInvocation:] and -[NSObject methodSignatureForSelector:] though you will have to use method syntax to call these methods and it can get complicated if you want to use primitive type properties.
you can generate types dynamically using ivars and methods, but there is not a means to get all the functionality of a declared property via one or two runtime calls.
a handful of functions should be all that is needed to accomplish the common routines, but a complete implementation would require some work and some syntactical noise.