From a weak reference to the crash talk weak assign strong application Scenario "iOS development tutorial"

<title>From a weak reference to the crash talk weak assign strong application scenario</title>

Method One of the definitions in. h:

@property(nonatomic,assign)NSArray*dataSource;

Define method Two

@property(nonatomic,strong)NSArray*dataSource;

How to implement in. m

- (void)Viewdidload {    [Super Viewdidload];    if (YES) {        Nsarray *array = @[@ "1", @ "2", @ "3"];        Self.datasource = Array;    }     if (Self.dataSource.count > 2) {        NSLog (@ "Self.datasource can I print?" Can print instructions can be defined as assign ");    }}

Results. H method? Crash, method? can be executed,

But what if it's a way to solve it?

- (void)Viewdidload {    [Super Viewdidload];    if (YES) {        Nsarray *array = @[@ "1", @ "2", @ "3"];        Self.datasource = [Array copy];    }     if (Self.dataSource.count > 2) {        NSLog (@ "Self.datasource can I print?" Can print instructions can be defined as assign ");    }}

Or

- (void)Viewdidload {    [Super Viewdidload];    if (YES) {        Nsarray *array = @[@ "1", @ "2", @ "3"];        Self.datasource = [Nsarray Arraywitharray:array];    }     if (Self.dataSource.count > 2) {        NSLog (@ "Self.datasource can I print?" Can print instructions can be defined as assign ");    }}

In short, these two improvements, and strong a truth, strong is in the setter, on the right side of the equal value of the strong operation, then why the above Self.datasource changed to _datasource also do not cause a crash? The _datasource compiler generated the setter method automatically and generated the _datasource Ivar variable, pointing to the same memory area.

At the same time, it can be seen that strong also affect the _datasource assignment. It's more intuitive to look at the MRC:

The setter of Arc

// _age的setter和getter- (void)setAge:(int)age{ _age = age;}

MRC Setter

//@property (nonatomic, retain) nsstring *name;- (void)SetName:(NSString *)name{    if (_name != name) {        [_name release];        _name = [Name retain];    }}

//@property (nonatomic, copy) NSString *name;- (void)SetName:(NSString *)name{    if (_name != name) {        [_name release];        _name = [Name copy];    }}

From a weak reference to the crash talk weak assign strong application Scenario "iOS development tutorial"