CODEWITHSUNDEEP
iosobjective-cuiviewsuper
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Reputation: 27

iOS: UIView subclass init will call [super init] then call methods in super class, why it will call [subclass initWithFrame:xx]?

I am confused with [UIView init] and [UIView initWithFrame:xx], after i search the stackoverflow and i found below questions and answers：

Why do both init functions get called

iOS: UIView subclass init or initWithFrame:? then i konw the initwithFrame is the designed initializer, what make me confused with the answer is when we call [myview init](myView is subclass of UIView and overwrite init and initwithfrme:), it will call call [super init] then it will call [super initWithFrame:xx] as super will find methods in super class, why it will call [myView initWithFrame:xx]???

Upvotes: 1

Views: 456

Answers (2)

john_ryan
john_ryan

Reputation: 1787

Since initWithFrame: is the designated initializer, apple's implementation of init (which you call when you call [super init]) internally calls the initWithFrame: function and passes in CGRectZero. That is the reason both get called. So the end flow ends up looking like this:

[YourClass init] -> [super init] -> [self initWithFrame:CGRectZero] -> 
[YourClass initWithFrame:CGRectZero] -> [super initWithFrame:CGRectZero]

This is assuming you call [super init] when you override init in YourClass and [super initWithFrame:] when you override initWithFrame.

Upvotes: 3

newacct
newacct

Reputation: 122439

it will call call [super init] then it will call [super initWithFrame:xx] as super will find methods in super class, why it will call [myView initWithFrame:xx]???

No. There is no such thing is super. super is just a syntax to allow you to call a method on self, using a different method lookup mechanism. Here, the [super init] call will lookup to the method -[UIView init] which is called on your object (the one self points to). Inside -[UIView init], it has a call [self initWithFrame:], which again, is called on your object (the one self points to). Here it does not use super, so the normal method lookup mechanism is used (the superclass of UIView doesn't have -initWithFrame: anyway). The normal method lookup mechanism finds the most overridden implementation in the class of the object. Since your class (the class of your object) overrides -initWithFrame:, the method it looks up to is -[YourClass initWithFrame:].

Upvotes: 0

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