在 Objective-C 中，我想知道方法定义旁边的 + 和 - 符号是什么意思。

- (void)loadPluginsAtPath:(NSString*)pluginPath errors:(NSArray **)errors;

最佳答案

+ 用于类方法，- 用于实例方法。

例如

// Not actually Apple's code.
@interface NSArray : NSObject {
}
+ (NSArray *)array;
- (id)objectAtIndex:(NSUInteger)index;
@end

// somewhere else:

id myArray = [NSArray array];         // see how the message is sent to NSArray?
id obj = [myArray objectAtIndex:4];   // here the message is sent to myArray

// Btw, in production code one uses "NSArray *myArray" instead of only "id".

有another question dealing with the difference between class and instance methods .

https://stackoverflow.com/questions/2097294/