ios属性关键字(assign、copy、retain、nonatomic)
2016-08-25 14:21
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只是大概的说明一下属性关键字的意思,详细的介绍,那需要你到网上具体查找,这里简单介绍,主要还是怎么使用这几个关键字,定义一些属性字段,需要使用哪些关键字,下面说的很明确,我们常用的几个。
nonatomic:
非原子性访问,对属性赋值的时候不加锁,多线程并发访问会提高性能。如果不加此属性,则默认是两个访问方法都为原子型事务访问。
例如:
[objc] view
plain copy
@property (nonatomic, assign) int number;
assign:
简单赋值,不更改索引计数,对数据类型 (如NSInteger,CGFloat, int, float, double, char, 等)。
例如:
[objc] view
plain copy
@property (nonatomic, assign) float number;
对于简单的数据类型,我们就使用assign关键字属性。
copy:
建立一个索引计数为1的对象,然后释放旧对象,作用于:NSString。
例如:
[objc] view
plain copy
@property (nonatomic, copy) NSString *myText;
retain
释放旧的对象,将旧对象的值赋予输入对象,再提高输入对象的索引计数为1。
例如:
[objc] view
plain copy
@property (nonatomic, retain) UIButton *mybutton;
ios的控件(UIView、等),那就使用retain关键字属性。
nonatomic:
非原子性访问,对属性赋值的时候不加锁,多线程并发访问会提高性能。如果不加此属性,则默认是两个访问方法都为原子型事务访问。
例如:
[objc] view
plain copy
@property (nonatomic, assign) int number;
assign:
简单赋值,不更改索引计数,对数据类型 (如NSInteger,CGFloat, int, float, double, char, 等)。
例如:
[objc] view
plain copy
@property (nonatomic, assign) float number;
对于简单的数据类型,我们就使用assign关键字属性。
copy:
建立一个索引计数为1的对象,然后释放旧对象,作用于:NSString。
例如:
[objc] view
plain copy
@property (nonatomic, copy) NSString *myText;
retain
释放旧的对象,将旧对象的值赋予输入对象,再提高输入对象的索引计数为1。
例如:
[objc] view
plain copy
@property (nonatomic, retain) UIButton *mybutton;
ios的控件(UIView、等),那就使用retain关键字属性。
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