编译器错误NSMutableDictionary for MultiTouchEvents

Question

我正在尝试使用NSMutableDictionary来存储4次触摸的X和Y值，如Apple的事件处理指南所示(http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/Introduction/Introduction.html)

我的代码是：

- (void)cacheBeginPointForTouches:(NSSet *)touches {
if ([touches count] > 0) {
    for (UITouch *touch in touches) {
        CGPoint *point = (CGPoint *)CFMutableDictionaryGetValue(_TouchesDict, touch);
        if (point == NULL) {
            point = (CGPoint *)malloc(sizeof(CGPoint));
            CFDictionarySetValue(_TouchesDict, touch, point);
        }
        *point = [touch locationInView:_view.superview];
    }
}
}

然而，我不断收到这样的编译器错误：

Undefined symbols for architecture i386:
  "_CFMutableDictionaryGetValue", referenced from:
  -[ViewController cacheBeginPointForTouches:] in ViewController.o
  "_OBJC_IVAR_$_UIViewController._view", referenced from:
  -[ViewController cacheBeginPointForTouches:] in ViewController.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

有人对我可能做错了什么有什么建议吗？

谢谢！

Answer 1

用CFDictionaryGetValue替换CFMutableDictionaryGetValue。CFMutableDictionaryGetValue函数对我来说似乎很奇怪。我认为它不存在