为什么xcode的方法前面会有+-号?

Question

xcode经常有一些函数前面有＋－号。请问这是什么意思？怎么用？谢谢！
本小白不胜感激！
比如：
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
//This means the application has been terminated
}

+ (NSParagraphStyle *)defaultParagraphStyle;
+ (NSWritingDirection)defaultWritingDirectionForLanguage:(NSString *)languageName; // languageName is in ISO lang region format

Answer 1

+方法即类方法类方法是属于类对象的，所以无需创建类的实例对象我们就可以直接使用它们。使用形式为：[ClassName classMethod];对此你可以搜索一下Objective-C 类方法的相关内容，多看几篇博客教程相信你会对它有更好的理解