NSInvocationOperation GUNStep源码

NSOperation GUNStep源码
NSInvocationOperation GUNStep源码
NSOperationQueue GUNStep源码

NSInvocationOperation只是对NSOperation的简单封装,专注于操作
两种方式初始化,但都是把要做的操作封装成 NSInvocation 对象

- (id) initWithInvocation: (NSInvocation *)inv
{
  if (((self = [super init])) != nil)
    {
      [inv retainArguments];
      _invocation = [inv retain];
    }
  return self;
}

- (id) initWithTarget: (id)target selector: (SEL)aSelector object: (id)arg
{
  NSMethodSignature *methodSignature;
  NSInvocation *inv;

  methodSignature = [target methodSignatureForSelector: aSelector];
  inv = [NSInvocation invocationWithMethodSignature: methodSignature];
  [inv setTarget: target];
  [inv setSelector: aSelector];
  if ([methodSignature numberOfArguments] > 2)
    [inv setArgument: &arg atIndex: 2];
  return [self initWithInvocation: inv];
}

main 方法

- (void) main
{
  if (![self isCancelled])
    {
      NS_DURING
    [_invocation invoke]; // 简单的执行了 _invocation 封装的方法
      NS_HANDLER
    _exception = [localException copy];
      NS_ENDHANDLER
    }
}

操作返回值

- (id) result
{
  id result = nil;

  if (![self isFinished]) // 如果还没执行完
    {
      return nil;
    }
  if (nil != _exception) // 如果执行操作的时候有异常
    {
      [_exception raise];
    }
  else if ([self isCancelled]) // 如果任务取消了,就抛出异常
    {
      [NSException raise: (id)NSInvocationOperationCancelledException
        format: @"*** %s: operation was cancelled", __PRETTY_FUNCTION__];
    }
  else // 通过 _invocation 的执行结果返回值
    {
      const char *returnType = [[_invocation methodSignature] methodReturnType];

      if (0 == strncmp(@encode(void),
        GSSkipTypeQualifierAndLayoutInfo(returnType), 1))
    {
      [NSException raise: (id)NSInvocationOperationVoidResultException
            format: @"*** %s: void result", __PRETTY_FUNCTION__];
    }
      else if (0 == strncmp(@encode(id),
        GSSkipTypeQualifierAndLayoutInfo(returnType), 1))
    {
      [_invocation getReturnValue: &result];
    }
      else
    {
      unsigned char *buffer = malloc([[_invocation methodSignature]
                       methodReturnLength]);

      [_invocation getReturnValue: buffer];
      result = [NSValue valueWithBytes: buffer objCType: returnType];
    }
    }
  return result;
}

总结: NSInvocationOperation是对NSOperation的简单封装, 持有了一个NSInvocation对面,在main方法里调用.

GUNStep里没有 NSBlockOperation的代码, 不能粘出来学习了,哎,忧伤