OC中self.a與_a的用法

Person.m

@interface Person : NSObject
@property(nonatomic,copy)NSString *name;
@property(nonatomic,copy)NSString *sex;

-(void)changeNameValue:(NSString*)newName andsexvalue:(NSString*) sexvalue;
@end

-(void)changeNameValue:(NSString *)newName andsexvalue:(NSString *)sexvalue{
    self.name=newName;
    _sex=sexvalue;
}

controller.m

 NSMutableString *newname=[NSMutableString stringWithFormat:@"tony"];
    NSMutableString *newsex=[NSMutableString stringWithFormat:@"man"];
    
    Person *xiaoming = [[Person alloc] init];
    [xiaoming changeNameValue:newname andsexvalue:newsex];
    
    NSLog(@"xiaoming newName: %@, newSex: %@;", xiaoming.name, xiaoming.sex);
    
    [newname appendString:@"Good"];
    [newsex appendString:@"andwoman"];
    NSLog(@"To observe the changes ： xiaoming name: %@, sex: %@;", xiaoming.name, xiaoming.sex);

結果如下：

Person中的方法self.使用的是深拷貝，_sex使用的是淺拷貝。當controller中newname添加新內容不會影響到其他類的屬性，_sex的淺拷貝會隨着調用該屬性的變量一起改變。因爲self.會生成getter與setter方法，_a並不會生成getter與setter方法。