如何将@selector作为参数传递?

For the method:

的方法:

[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.

如何传入@selector?我尝试将它强制转换为(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，我有这样一个方法:

+(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。如何在不崩溃的情况下传入选择器，以便当线程准备好时，新线程可以调用选择器?

5 个解决方案

#1

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，而是将选择器传递给预期的对象。要将非对象值作为对象传递，可以使用NSValue。在这种情况下，您需要创建一个接受NSValue并检索适当选择器的方法。这里有一个例子实现:

@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

#2

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 NSInvocation to 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，如果您不想更改方法，您可以创建一个nsincall来为您的方法调用创建一个调用(因为它可以用非对象参数设置调用)，然后调用它do [NSThread detachNewThreadSelector:@selector:@selector(调用)toTarget:myInvocation withObject:nil];

#3

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打算作为任意非对象类型的对象包装器。

#4

Please see: passing a method as an argument

请参见:传递一个方法作为参数

#5

If you don't want to specify an object just use nil.

如果不想指定对象，就使用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.

如果需要将一个对象传递给选择器，它应该是这样的。

Here I'm passing a string to the method "setText".

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]; 
}

#1

@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

#2