objective-c - Objective C 程序未编译

Question

我目前正在我的电脑上学习 objective-c ，我的程序无法编译。这是我得到的错误。 “Interface.m:在函数'-[Person print]'中:Interface.m:17:2:error:找不到'NXConstantString'的接口(interface)声明”

我正在使用 gcc 编译器。

这是我的程序

 #import <Foundation/NSObject.h>
 #import <stdio.h>

@interface Person : NSObject {
    int age;
    int weight;
}

-(void) print;
-(void) setAge: (int) a;
-(void) setWeight: (int) w;

@end    

@implementation Person
-(void) print {
    printf(@"I am %i years old and I weigh about %i pounds",age,weight);
}
-(void) setAge: (int) a{
    age = a;
}
-(void) setWeight: (int) w{
    weight = w;
}
@end 

int main(int argc, char * argv[]){

    Person *person;

    person = [Person alloc];    
    person = [person init];

    [person setAge: 16];
    [person setWeight: 120];
    [person print];
    [person release];

    return 0;

}

Answer 1

文字字符串，例如 @"I am %i years old and I weigh about %i pounds"是(默认)类型NSConstantString但是您没有导入声明该类的头文件。

您可以添加:

#import <Foundation/NSString.h>

或者简单地导入 Foundation 框架中的所有 header :

#import <Foundation/Foundation.h>

编辑:我刚刚注意到您使用 Objective-C 字符串作为 printf() 的参数。 :

printf(@"I am %i years old and I weigh about %i pounds",age,weight);

那是不对的; printf()需要一个 C 字符串，例如:

printf("I am %i years old and I weigh about %i pounds",age,weight);

您也可以使用 NSLog() ，它确实需要一个 Objective-C 字符串:

NSLog(@"I am %i years old and I weigh about %i pounds",age,weight);