从[[class alloc] init]返回nil是否被视为良好实践？

问题描述

这是一个常见的成语在Objective-C。

And is it a common idiom in Objective-C.

我只看到这个使用[[NSImage alloc] initWithContentsOfFile：str]我认为有一个内存泄漏，因为我调用alloc和咒语是：
调用alloc，你必须调用release - 除非你不需要的情况下。

I've only seen this used on [[NSImage alloc] initWithContentsOfFile: str] and it always make me think there is a memory leak, because i called alloc and the mantra is:"Call alloc and you must call release" - unless its one of the cases where you don't need to.

推荐答案

这是一个常见的成语，表示初始化对象时出现错误。你是正确的，但是，分配的实例必须被释放。所以模式是

It is a common idiom to indicate a error in initializing the object. You are correct, however, the allocated instance must be released. So the pattern would be

- (id)init
{
  self = [super init];
  if(self != nil) {
    //... do init
    if(errorInInit) {
      [self release];
      return nil;
    }
  }

  return self;
}

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