如何从 NSInvocable 中获取 NSString 结果？
下面的代码按预期工作：
NSLog(@"%@", [NSString stringWithString:@"test"]; // Logs "test"
但是当我用 NSInitation 替换它时，我得到了完全不同的结果：
Class class = [NSString class];
SEL selector = @selector(stringWithString:);
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:
[class methodSignatureForSelector:selector]];
[invocation setTarget:class];
[invocation setSelector:selector];
[invocation setArgument:@"test" atIndex:2];
[invocation invoke];
id returnValue = nil;
[invocation getReturnValue:&returnValue];
NSLog(@"%@", returnValue); // Logs "NSCFString"
我已经搜索了高低，但无法弄清楚这一点。有什么帮助吗？谢谢！
The following code works as expected:
NSLog(@"%@", [NSString stringWithString:@"test"]; // Logs "test"
But when I replace it with an NSInvocation, I get a totally different result:
Class class = [NSString class];
SEL selector = @selector(stringWithString:);
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:
[class methodSignatureForSelector:selector]];
[invocation setTarget:class];
[invocation setSelector:selector];
[invocation setArgument:@"test" atIndex:2];
[invocation invoke];
id returnValue = nil;
[invocation getReturnValue:&returnValue];
NSLog(@"%@", returnValue); // Logs "NSCFString"
I've searched high and low, but cannot figure this out. Any help? Thanks!
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来自 NSIncation 类参考：
当参数值是一个对象时，传递一个指向应从中复制该对象的变量（或内存）的指针：
由于 @"test" 实际上是构造 NSString 的实例，因此您应该使用
From the NSInvocation class reference:
When the argument value is an object, pass a pointer to the variable (or memory) from which the object should be copied:
Since @"test" is actually constructing an instance of NSString, you should use