objective-c - 在iOS中调用方法有什么区别

Question

假设我打电话给

[self methodname] 

和其他的

[self performSelector:@selector(methodname) withObject:nil];

Answer 1

没有任何区别。

直接来自文档performSelector:

该performSelector:方法相当于aSelector直接向接收者发送消息。例如，以下所有三个消息都执行相同的操作：

id myClone = [anObject copy];
id myClone = [anObject performSelector:@selector(copy)];
id myClone = [anObject performSelector:sel_getUid("copy")];

尽管在特定情况下没有区别，但是存在的原因performSelector:是它允许调用在编译时可能不可用的任意选择器，如文档中所述：

但是，该performSelector:方法允许您发送直到运行时才确定的消息。变量选择器可以作为参数传递：

SEL myMethod = findTheAppropriateSelectorForTheCurrentSituation();
[anObject performSelector:myMethod];

上述考虑也适用于这两种变体performSelector:withObject:，performSelector:withObject:withObject:.

另请注意，这不适用于另一组方法，即

• performSelector:withObject:afterDelay:
• performSelector:withObject:afterDelay:inModes:
• performSelectorOnMainThread:withObject:waitUntilDone:
• performSelectorOnMainThread:withObject:waitUntilDone:modes:
• performSelector:onThread:withObject:waitUntilDone:
• performSelector:onThread:withObject:waitUntilDone:modes:
• performSelectorInBackground:withObject:

此处的更多信息：performSelector 是立即执行还是计划执行？

Answer 2

[self methodname]` is shorter and easier to read, write and comprehend.

[self performSelector:@selector(methodname) withObject:nil]` makes it possible to execute arbitrary selectors. If you save the selector in a variable, then you can execute it later on without knowing the method you invoke.

//Self works like this in oops and self works as setter for your class. It also indicates that u r using getter and setter method.