面向对象编程增加间接层对程序的扩展

一下通过代码做出解释：

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        NSLog(@"The numbers forme 1 to 5");
        for(int i = 1; i <= 5; i++)
        {
             NSLog(@"%d\n", i);
        }
    }
    return 0;
}

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        int count = 5;
        NSLog(@"The numbers forme 1 to %d", count);
        for(int i = 1; i <= count; i++)
        {
             NSLog(@"%d\n", i);
        }
    }
    return 0;
}

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        int fist = 1, count = 5;
        NSLog(@"The numbers forme %d to %d", fist, count);
        for(int i = fist; i <= count; i++)
        {
             NSLog(@"%d\n", i);
        }
    }
    return 0;
}

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        int fist, count;
        scanf("%d %d", &fist, &count);
        NSLog(@"The numbers forme %d to %d", fist, count);
        for(int i = fist; i <= count; i++)
        {
             NSLog(@"%d\n", i);
        }
    }
    return 0;
}

请观察以上代码，发现是怎么一步一步的对程序扩展的，相信你就的增加一个间接层就有所了解了。