xcode 未声明的标识符目标 C
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Undeclared identifier Objective C
提问by ukbaz
I can't seem to get round this error; use of undeclared identifier 'ageBy'. I dont understand why am getting it as i have the import Person.h in my code. Thanks for your time and any help.
我似乎无法解决这个错误；使用未声明的标识符“ageBy”。我不明白为什么要得到它，因为我的代码中有导入 Person.h。感谢您的时间和任何帮助。
Person.h
人.h
@interface Person : NSObject
{
int _age;
int _years;
NSString *_name;
NSString *_job;
}
-(void)setAge:(int)age;
-(int)age;
-(void)setName:(NSString *)name;
-(NSString *)name;
-(void)setJob:(NSString *)job;
-(NSString *)job;
-(NSString *)summaryString;
-(void)ageBy:(int)years;
@end
Person.m
人.m
#import "Person.h"
@implementation Person
-(void)setAge:(int)age{
_age = age;
}
-(int)age{
return _age;
}
-(void)setName:(NSString *)name{
_name = name;
}
-(NSString *)name{
return _name; }
-(void)setJob:(NSString *)job{
_job = job;
}
-(NSString *)job{
return _job;
}
-(NSString *)summaryString{
return [NSString stringWithFormat:@"The Person %@ is %d years old and is a %@",_name,_age,_job];
-(void)ageBy:(int)years{
_years = years;
_age = years + _age;
}
}
@end
回答by Tommy
Your ageBy:is defined inside summaryString. You probably want to move the curly bracket just before @endso that it is above -(void)ageBy:(int)years. So:
你ageBy:是在里面定义的summaryString。您可能想在之前移动大括号@end，使其位于-(void)ageBy:(int)years. 所以：
-(NSString *)summaryString{
return [NSString stringWithFormat:@"The Person %@ is %d years old and is a %@",_name,_age,_job];
}
-(void)ageBy:(int)years{
_years = years;
_age = years + _age;
}
Also as a style note, if summaryStringis merely for debugging then you'd possibly be better off declaring it as description. The latter is the standard form for getting an implementation-dependand string description of an Objective-C object, with the net effect that collection objects like NSArrayknow to call descriptionon all their child objects in order to create the correct output.
同样作为样式说明，如果summaryString仅用于调试，那么最好将其声明为description. 后者是获取 Objective-C 对象的依赖于实现的字符串描述的标准形式，其最终效果是集合对象NSArray知道调用description其所有子对象以创建正确的输出。
回答by rmaddy
As was stated, the problem is caused by the ageBy:method being embedded in the summaryStringmethod.
如前所述，问题是由ageBy:方法中嵌入的summaryString方法引起的。
I wanted to demonstrate how this class could be written using modern Objective-C:
我想演示如何使用现代 Objective-C 编写此类：
// Person.h
@interface Person : NSObject
@property (nonatomic, assign) int age;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *job;
- (void)ageBy:(int)years;
@end
// Person.m
@implementation Person
- (NSString *)description {
return [NSString stringWithFormat:@"The Person %@ is %d years old and is a %@", self.name, self.age, self.job];
}
- (void)ageBy:(int)years {
self.age = self.age + years;
}
@end
