iOS key words

Self: Similar to the this pointer in Java, is a shadow parameter, pointing to the class of the currently calling method

Super: Calling methods of the parent class

if (Self=[super init]), is a general notation, the assignment and measurement of 0 is to prevent the superclass in the initialization process changes, return different objects, and the implementation of the parent class related to the initialization of resources.

Atomic: Atomic access, which is locked when the property is assigned a value. When setting the @property property, the default is atomic, which provides multithreading security

Nonatomic: Non-atomic access, no lock on attribute assignment. Multi-threaded concurrent access improves performance, but variables are easily modified to make the program crash

Assign: Simple assignment, without changing the index count. Applies to the underlying data type, such as NSNumber

Copy: Creates a new object with an index count of 1 and releases the old object. This property is used only for objects that implement the <NSCoding> protocol.

Retain: Similar to copy, creates a new object with an index count of 1 and releases the old object. Retain is a copy pointer, copy creates a new memory and then makes a value reference. For complex data types, such as Nsarray, the effect is approximate. Although copy creates a new memory, each element in the array is simply a pointer to the element that was copied.

iOS key words