什么是Objective-C中获取可空bool的方法?

How should I go about getting a bool value that I can assign true, false and nil to in Objective-C? What is the Objective-C way of doing this? Much like C#'s Nullable.

我应该如何获得一个bool值我可以在Objective-C中赋给true, false和nil ?Objective-C是什么意思?就像c#可以为空。

I'm looking to be able to use the nil value to represent undefined.

我想用nil值来表示未定义的。

2 个解决方案

#1

An NSNumber instance might help. For example:

NSNumber实例可能会有所帮助。例如:

NSNumber *yesNoOrNil;

yesNoOrNil = [NSNumber numberWithBool:YES]; // set to YES
yesNoOrNil = [NSNumber numberWithBool:NO];  // set to NO
yesNoOrNil = nil; // not set to YES or NO

In order to determine its value:

为了确定其值:

if (yesNoOrNil == nil)
{
    NSLog (@"Value is missing!");
}
else if ([yesNoOrNil boolValue] == YES)
{
    NSLog (@"Value is YES");
}
else if ([yesNoOrNil boolValue] == NO)
{
    NSLog (@"Value is NO");
}

On all Mac OS X platforms after 10.3 and all iPhone OS platforms, the -[NSNumber boolValue] method is guaranteed to return YES or NO.

在10.3之后的所有Mac OS X平台和所有iPhone OS平台上，-[NSNumber boolValue]方法保证返回YES或NO。

#2

I think you will need to use some class for that, e.g. wrap bool to NSNumber object.

我认为您需要使用一些类，例如将bool包装到NSNumber对象。

#1