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在objective-c中atomic和nonatomic有什么區(qū)別？retain有什么用？

高洛峰 2017-04-21 10:57:07

539

比如下面的代碼

@property(nonatomic, retain) UITextField *userName;
@property(atomic, retain) UITextField *userName;

他們有啥區(qū)別，retain在這里起啥作用

高洛峰

擁有18年軟件開發(fā)和IT教學(xué)經(jīng)驗(yàn)。曾任多家上市公司技術(shù)總監(jiān)、架構(gòu)師、項(xiàng)目經(jīng)理、高級(jí)軟件工程師等職務(wù)。網(wǎng)絡(luò)人氣名人講師，...

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左手右手慢動(dòng)作2017-04-21 10:59:07 4 floor

retain is to add 1 to the reference count of the attribute
The retain here means that this setter will add 1 to the reference count of the parameter. For example:

self.userName = uName;

At this time, the reference count of uName will be increased by 1.
However, SDK 5.0 and later supports ARC, which means automatic application counting. Therefore, there is no need to retain and copy when defining attributes. Instead, use strong to let ARC manage it.
An article providing apple core for reference: http://pingguohe.net/2011/08/05/llvm3...