Define a keyword for a property

1.strong: OC Object except Nsstring/block @property (nonatomic,strong) nsarray *< #model #>

2.weak: Various UI controls (but not absolute, there are controls to use the Strong property) @property (Nonatomic,weak) UIButton *button;

Basic data types such as 3.assign:cgfloat,nsinteger, enumerations, structs (non-OC Objects) @property (nonatomic,assign) CGFloat < #model #>;

4.copy: Immutable replicas (such as NSString, Nsarray, nsdictionary) are created mutablecopy: a mutable copy is created (such as nsmutablestring, Nsmutablearray, nsmutabledictionary) @property (nonatomic,copy) nsstring *< #model #>;

• @property the selection of memory management policies

1. Non-arc

1> copy: only for Nsstring/block

2> retain: OC object except Nsstring/block

3> Assign: Basic data type, enumeration, struct (non-OC object), when 2 objects are referenced to each other, one end with retain, one end with assign

2.arc

1> copy: only for Nsstring/block

2> Strong: OC Object except Nsstring/block

3> Weak: When 2 objects are referenced to each other, one end with strong, the other end with weak

4> assgin: Basic data type, enumeration, struct body (non-OC object)

Define a keyword for a property