Objective-C无法设置类/对象变量

Question

我试图让这段代码工作,但似乎无法获得任何显示变量设置的输出:

#import <Foundation/Foundation.h>
#import "thingy.h"

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

@autoreleasepool {

thingy *mythingy;

    [mythingy setMass:75.00];
    [mythingy setTime:5.00];

    NSLog(@"mass of mythingy = %f kg", [mythingy mass]);
    NSLog(@"time of mythingy = %f sec", [mythingy time]);

    }
return 0;
}

这是我得到的输出:

mass of mythingy = 0.000000 kg
time of mythingy = 0.000000 sec

我也尝试不使用@autoreleasepool(ARC),代码如下所示,但输出与以前相同:

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    thingy *mythingy;

    [mythingy setMass:75.00];
    [mythingy setTime:5.00];

    NSLog(@"mass of mythingy = %f kg", [mythingy mass]);
    NSLog(@"time of mythingy = %f sec", [mythingy time]);

[mythingy release];
[pool drain];

更新:

好吧所以我采取了以前的代码,并添加了一行,它现在看起来像这样,但是令人沮丧,因为我想使用ARC !!!!

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
thingy *mythingy = [[thingy alloc]init];

    [mythingy setMass:75.00];
    [mythingy setTime:5.00];

    NSLog(@"mass of mythingy = %f kg", [mythingy mass]);
    NSLog(@"time of mythingy = %f sec", [mythingy time]);

[mythingy release];
[pool drain];

输出此代码:

mass of mythingy = 75.000000 kg
time of mythingy = 5.000000 sec

Answer 1

您必须先创建一个对象(mythingy)才能使用它.尝试更改thingy *mythingy;为thingy *mythingy = [mythingy new];或使用自定义方法初始化它(如果已实现).