What does weak mean in Objective-C?

What does weak mean in Objective-C?

weak specifies a reference that does not keep the referenced object alive. A weak reference is set to nil when there are no strong references to the object.

Is C and Objective-C similar?

The main difference in C and Objective C is that C is a procedure programming language which doesn’t support the concepts of objects and classes and Objective C is Object-oriented language which contains the concept of both procedural and object-oriented programming languages.

What is strong reference and weak reference in Objective-C?

Objective-C uses reference counting to manage the memory of its objects through the concept of object ownership. There are two types of object reference: Strong references, which keep an object “alive” in memory. Weak references, which have no effect on the lifetime of a referenced object.

What’s the difference between weak and strong?

The key difference between a strong and a weak or unowned reference is that a strong reference prevents the class instance it points to from being deallocated. In other words, weak and unowned references cannot prevent a class instance from being deallocated.

What is difference between weak and strong?

What is difference between weak and unowned?

The main difference between weak and unowned is that weak is optional while unowned is non-optional. By declaring it weak you get to handle the case that it might be nil inside the closure at some point. If you try to access an unowned variable that happens to be nil, it will crash the whole program.

What is the difference between __Block and __weak in C++?

A weak reference is set to nil when there are no strong references to the object. So they are technically different things. __block is to stop your variable being copied from your external scope into your block scope. __weak is a self delimiting weak pointer. Note I said technically, because for your case they will do (almost) the same thing.

What are weak symbols in C++?

Weak symbols are not mentioned by C or C++ language standards; as such, inserting them into code is not very portable. Even if two platforms support the same or similar syntax for marking symbols as weak, the semantics may differ in subtle points, e.g. whether weak symbols during dynamic linking at runtime lose their semantics or not.

What is ____weak function and how to write it?

__weak function are methods that can be overwritten by user function with same name, used to define vector tables, and default handlers Normal function writing (declaration and definition) are considered strong meaning that the function name cannot be re declared, you will get compiler/linker error

What is the difference between __weak and __block in Swift?

If your project uses ARC and is only for iOS4.3 and above, use __weak. It ensures the reference is set to nil if the global scope reference is releases somehow. If your project doesn’t use ARC or is for older OS versions, use __block.