objective-c – 获取“未找到方法定义错误”并且不知道原因

我正在通过Objective-C进行Apple的编程,并在此过程中进行非常简单的练习.出于某种原因,我收到一条错误,指出无法找到方法定义.我检查了拼写和大写,方法是在.h和.m文件中.无法弄清楚它为什么这样做.

具体来说,无法找到“Say Something”的方法定义.这是代码：

.H

#import <Foundation/Foundation.h>

@interface XYZPerson : NSObject

@property NSString *firstName;
@property NSString *lastName;
@property NSDate *dateOfBirth;

- (void)saySomething;
- (void)sayHello;
- (void)sayShutUp;
- (void)sayHola;
+ (id)person;


@end

还有他们

#import "XYZPerson.h"

@implementation XYZPerson


- (void)saySomething:(NSString *)greeTing {
    NSLog(@"%@",greeTing);
}

- (void)sayHello {
[self saySomething:@"Hello,World!"];
}

- (void)sayHola {
[self saySomething:@"Hola,Amigos!"];
}
- (void)sayShutUp {
[self saySomething:@"Shut up!"];
}
+ (id)person {
return [[self alloc]init];
}


@end

- (void)saySomething;

- (void)saySomething:(NSString *)greeTing;