@synthesize 创建什么 UIView setter
如何制作自定义 UIView setter。例如：
1）我们创建属性：
@property (retain) IBOutlet UILabel *myLabel
2）我们创建setter（与@synthesize创建的相同）：
- (void)setMyLabel:(UILabel *)anObject
{
[myLabel release];
myLabel = [anObject retain];
}
是否正确，或者我应该检查新视图是否与当前视图不同
- (void)setMyLabel:(UILabel *)anObject
{
if(anObject != myView){
[myLabel release];
myLabel = [anObject retain];
}
}
Just myView and anObject are object指针。那么我们应该用 -isEqual 方法检查它们吗？或者我们根本不需要检查它？ @synthesize 默认生成什么代码？
谢谢。
How to make custom UIView setter. For example:
1) We create property:
@property (retain) IBOutlet UILabel *myLabel
2) we make setter (the same as @synthesize would create):
- (void)setMyLabel:(UILabel *)anObject
{
[myLabel release];
myLabel = [anObject retain];
}
Is it correct, or should I check if the new view are not the same as the current with
- (void)setMyLabel:(UILabel *)anObject
{
if(anObject != myView){
[myLabel release];
myLabel = [anObject retain];
}
}
Just myView and anObject are object pointers. So should we check them with -isEqual method then? Or we don't need to check it at all? What code does @synthesize generates by defaults?
Thanks.
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只有第二个版本（带有
if语句）是正确的。在您的第一个版本中，假设anObject和myLabel实际上指向同一个对象（即指针是相同的）。在这种情况下，您将释放该对象，如果没有其他对象保留该对象，这将导致该对象被释放。随后尝试保留已释放的对象将导致崩溃。Only the second version (with the
ifstatement) is correct. In your first version, imagine thatanObjectandmyLabelactually point to the same object (i.e., the pointers are the same). In that case, you would release the object, which would cause it to be deallocated if no other object had retained it. The subsequent attempt to retain the deallocated object would cause a crash.