iOS-语法syntax

#import <Foundation/Foundation.h>

@interface People : NSObject

@property (nonatomic,copy) NSString * run;
@property (nonatomic,copy) NSString * sing;
@end

@implementation People
@synthesize run;//可写可不写
@synthesize sing;//可写可不写
@end

可写的话 使用的是 run
不写的话 使用的是 _run

@interface Student : People

@end

#import <Foundation/Foundation.h>

@interface People : NSObject

@property (nonatomic,copy) NSString * run;
@property (nonatomic,copy) NSString * sing;

@end
在h文件中申明成员变量
run 可以供子类调用和赋值

#import "People.h"
@interface People()
@property (nonatomic,copy) NSString * run;
@property (nonatomic,copy) NSString * sing;
@end

@implementation People
@end

成员变量定义在m文件 run 属性不能供子类调用赋值 
就会提示：Property ‘sing‘ not found on object of type ‘Student *‘