id<MyProtocol> topLayoutGuideObj = objc_msgSend(viewController, @selector(myselector));
“函数调用的参数过多,预期为 0,实际为 2”
但是,objc_msgSend 的函数签名如下所示:
#if !OBJC_OLD_DISPATCH_PROTOTYPES
OBJC_EXPORT void objc_msgSend(void /* id self, SEL op, ... */ )
__OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);
OBJC_EXPORT void objc_msgSendSuper(void /* struct objc_super *super, SEL op, ... */ )
__OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);
#else
/**
* Sends a message with a simple return value to an instance of a class.
*
* @param self A pointer to the instance of the class that is to receive the message.
* @param op The selector of the method that handles the message.
* @param ...
* A variable argument list containing the arguments to the method.
*
* @return The return value of the method.
*
* @note When it encounters a method call, the compiler generates a call to one of the
* functions \c objc_msgSend, \c objc_msgSend_stret, \c objc_msgSendSuper, or \c objc_msgSendSuper_stret.
* Messages sent to an object’s superclass (using the \c super keyword) are sent using \c objc_msgSendSuper;
* other messages are sent using \c objc_msgSend. Methods that have data structures as return values
* are sent using \c objc_msgSendSuper_stret and \c objc_msgSend_stret.
*/
OBJC_EXPORT id objc_msgSend(id self, SEL op, ...)
__OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);
参数是“void”还是可变参数?!我不明白我应该怎么调用它。
最佳答案
只看上面你提到的几行。
/*
* ...
*
* These functions must be cast to an appropriate function pointer type
* before being called.
*/
你可以这样调用它:
#import <objc/runtime.h>
#import <objc/message.h>
id<MyProtocol> topLayoutGuideObj = ((id (*)(id, SEL))objc_msgSend)(viewController, @selector(myselector));
或
id (*typed_msgSend)(id, SEL) = (void *)objc_msgSend;
id<MyProtocol> topLayoutGuideObj = typed_msgSend(viewController, @selector(myselector));
关于ios - 在 xcode6 gold master 中,使用 objc_msgSend 现在会抛出一个语法错误,指出参数数量错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25852079/