使用makeObjectsPerformSelector：withObject：使用false布尔值 [英] Using makeObjectsPerformSelector:withObject: with a false boolean

问题描述

我有一个 UITextField 数组 _fields 。我想要能够立刻向他们发出消息，让它们突出显示，然后再做相同的操作，使突出显示属性为 NO 。这部分代码的工作原理。

I've got an array of UITextField objects called _fields. I want to be able to message them all at once to set them to be highlighted, and then do the same to turn that highlighted property to NO. This part of the code works.

[fields makeObjectsPerformSelector:@selector(setHighlighted:) withObject:@YES];

但这部分不会;我不能让它做任何事情。

This part, however, does not; I can't get it to do anything.

[fields makeObjectsPerformSelector:@selector(setHighlighted:) withObject:@NO];

但这样做有效。

for (UITextField *field in fields) {
    field.highlighted = NO;
}

我本来希望使用 makeObjectsPerformSelector：withObject：消息，但我没有得到太多的爱与 @NO 。

What gives? I would've liked to have used the makeObjectsPerformSelector:withObject: message, but I'm not getting much love with @NO. Can someone explain this behavior to me, or tell me if I'm doing something wrong?

推荐答案

setHighlighted：方法采用 BOOL 的类型。这不是对象类型。因此，您不能使用 makeObjectsPerformSelector：withObject：方法。

The setHighlighted: method takes a type of BOOL. This is not an object type. Therefore you can't use the makeObjectsPerformSelector:withObject: method.

$ c> @YES ，因为您正在传递指向 BOOL 参数的对象的指针。非零值被视为一个 YES 值。当你传递 @NO 时，你也传递一个指针。由于它也是一个非零值，它也被视为一个 YES 值。

It seems to work when passing @YES because you are passing a pointer to an object to the BOOL parameter. The non-zero value gets treated like a YES value. When you pass @NO you are also passing a pointer. Since it is also a non-zero value, it also gets treated like a YES value.

通过将 nil 传递给 withObject： NO >参数。 nil 值将为0，与 NO 相同。

You may get the desired effect of NO by passing nil to the withObject: parameter. The nil value will be 0 which is the same value as NO.

但是这些是kludges。请改用循环方法。

But these are kludges. Use the loop approach instead.

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