"No previous prototype for function" warning警告错误

在编译《iphone开发秘籍》第八章的秘诀一的代码时碰到以下警告错误：

CGPoint randomPoint()
{
    int half = 32;
    int freesize = 240 - 2 * half;
    return CGPointMake(random() % freesize + half, random() % freesize + half);
}

warning:No previous prototype for function "randomPoint"。如何取消这个警告错误呢？方法尝试了这两种都可以：

1.方法上加修饰符static

2.或者Project-Info -> TARGETS ->Build Settings -> LLVM GCC4.2 - Warnings组 -> Missing Function Prototypes   Yes->No