objective-c 如何将@selector 作为参数传递？
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How to I pass @selector as a parameter?
提问by erotsppa
For the method:
对于方法：
[NSThread detachNewThreadSelector:@selector(method:) toTarget:self withObject:(id)SELECTOR];
How do I pass in a @selector? I tried casting it to (id) to make it compile, but it crashes in runtime.
我如何传入@selector？我尝试将它转换为 (id) 以使其编译，但它在运行时崩溃。
More specifically, I have a method like this:
更具体地说，我有一个这样的方法：
+(void)method1:(SEL)selector{
[NSThread detachNewThreadSelector:@selector(method2:) toTarget:self withObject:selector];
}
It crashes. How do I pass in the selector without crashing, so that the new thread can call the selector when the thread is ready?
它崩溃了。如何在不崩溃的情况下传入选择器，以便新线程可以在线程准备好时调用选择器？
回答by Chuck
The problem here isn't passing a selector to a method, per se, but passing a selector where an object is expected. To pass a non-object value as an object, you can use NSValue. In this case, you'll need to create a method that accepts an NSValue and retrieves the appropriate selector. Here's an example implementation:
这里的问题不是将选择器传递给方法本身，而是在需要对象的地方传递选择器。要将非对象值作为对象传递，您可以使用NSValue. 在这种情况下，您需要创建一个接受NSValue的方法，并检索适当的选择器。这是一个示例实现：
@implementation Thing
- (void)method:(SEL)selector {
// Do something
}
- (void)methodWithSelectorValue:(NSValue *)value {
SEL selector;
// Guard against buffer overflow
if (strcmp([value objCType], @encode(SEL)) == 0) {
[value getValue:&selector];
[self method:selector];
}
}
- (void)otherMethodShownInYourExample {
SEL selector = @selector(something);
NSValue *selectorAsValue = [NSValue valueWithBytes:&selector objCType:@encode(SEL)];
[NSThread detachNewThreadSelector:@selector(methodWithSelectorValue:) toTarget:self withObject:selectorAsValue];
}
@end
回答by user102008
You can convert between selectors and string objects using the NSStringFromSelector()and NSSelectorFromString()functions. So you can just pass string objects instead.
您可以使用NSStringFromSelector()和NSSelectorFromString()函数在选择器和字符串对象之间进行转换。所以你可以只传递字符串对象。
Alternately, if you don't want to change your methods, you can create an NSInvocationto create an invocation for your method call (since it can set up invocations with non-object arguments), and then to call it do [NSThread detachNewThreadSelector:@selector(invoke) toTarget:myInvocation withObject:nil];
或者，如果您不想更改您的方法，您可以创建 anNSInvocation来为您的方法调用创建一个调用（因为它可以使用非对象参数设置调用），然后调用它 do[NSThread detachNewThreadSelector:@selector(invoke) toTarget:myInvocation withObject:nil];
回答by BJ Homer
Use NSValue, like so:
使用 NSValue，像这样：
+(void)method1:(SEL)selector {
NSValue *selectorValue = [NSValue value:&selector withObjCType:@encode(SEL)];
[NSThread detachNewThreadSelector:@selector(method2:)
toTarget:self
withObject:selectorValue];
}
NSValue is intended as an object-wrapper for arbitrary non-object types.
NSValue 旨在作为任意非对象类型的对象包装器。
回答by ennuikiller
Please see: passing a method as an argument
请参阅：将方法作为参数传递
回答by Brandon Schlenker
If you don't want to specify an object just use nil.
如果您不想指定对象，请使用 nil。
[NSThread detachNewThreadSelector:@selector(method:) toTarget:self withObject:nil];
If you need to pass an object to the selector it would look something like this.
如果您需要将一个对象传递给选择器，它看起来像这样。
Here I'm passing a string to the method "setText".
在这里，我将一个字符串传递给方法“setText”。
NSString *string = @"hello world!";
[NSThread detachNewThreadSelector:@selector(setText:) toTarget:self withObject:string];
-(void)setText:(NSString *)string {
[UITextField setText:string];
}
