未捕获的异常NSInvalidArgumentException

Question

我使用tutorialspoint.com编译目标c代码

@interface Foo{
@public
NSInteger x;
}
-(int) apple;
-(void)setAge:(NSInteger)number;
@end

@implementation Foo
-(int)apple{return 5;}

-(void)setAge:(NSInteger)number{
self->x=number+1;
NSLog(@"%d",self->x);
}
@end


int main (int argc, const char * argv[]){
NSAutoreleasePool *myPool = [[NSAutoreleasePool alloc] init];
Foo *p = [[Foo alloc] init];NSInteger nine = 9;
[p setAge:nine];
[myPool drain];
return 0;
}

，当我尝试编译时，我收到此编译错误：

main.m:41:3: warning: (Messages without a matching method signature   
main.m:41:3: warning: will be assumed to return 'id' and accept       
main.m:41:3: warning: '...' as arguments.)

Answer 1

您的班级Foo没有基类（即NSObject）。因此，此类不知道+alloc和-init。

@interface Foo : NSObject {
…