从 Objective-C 中的函数返回数组


Objective-C 编程语言不允许返回整个数组作为函数的参数。但是,您可以通过指定不带索引的数组名称来返回指向数组的指针。您将在下一章中学习指针,因此您可以跳过本章,直到您了解 Objective-C 中指针的概念。

如果要从函数返回一维数组,则必须声明一个返回指针的函数,如下例所示 -

int * myFunction() {
.
.
.
}

第二点要记住的是,Objective-C 不提倡将局部变量的地址返回到函数外部,因此您必须将局部变量定义为静态变量。

现在,考虑以下函数,它将生成 10 个随机数并使用数组返回它们,并按如下方式调用此函数 -

#import <Foundation/Foundation.h>

@interface SampleClass:NSObject
- (int *) getRandom;
@end

@implementation SampleClass

/* function to generate and return random numbers */
- (int *) getRandom {
   static int  r[10];
   int i;

   /* set the seed */
   srand( (unsigned)time( NULL ) );
   for ( i = 0; i < 10; ++i) {
      r[i] = rand();
      NSLog( @"r[%d] = %d\n", i, r[i]);
   }

   return r;
}

@end

/* main function to call above defined function */
int main () {
   
   /* a pointer to an int */
   int *p;
   int i;

   SampleClass *sampleClass = [[SampleClass alloc]init];
   p = [sampleClass getRandom];
   for ( i = 0; i < 10; i++ ) {
      NSLog( @"*(p + %d) : %d\n", i, *(p + i));
   }

   return 0;
}

当上面的代码一起编译并执行时,它会产生如下结果 -

2013-09-14 03:22:46.042 demo[5174] r[0] = 1484144440
2013-09-14 03:22:46.043 demo[5174] r[1] = 1477977650
2013-09-14 03:22:46.043 demo[5174] r[2] = 582339137
2013-09-14 03:22:46.043 demo[5174] r[3] = 1949162477
2013-09-14 03:22:46.043 demo[5174] r[4] = 182130657
2013-09-14 03:22:46.043 demo[5174] r[5] = 1969764839
2013-09-14 03:22:46.043 demo[5174] r[6] = 105257148
2013-09-14 03:22:46.043 demo[5174] r[7] = 2047958726
2013-09-14 03:22:46.043 demo[5174] r[8] = 1728142015
2013-09-14 03:22:46.043 demo[5174] r[9] = 1802605257
2013-09-14 03:22:46.043 demo[5174] *(p + 0) : 1484144440
2013-09-14 03:22:46.043 demo[5174] *(p + 1) : 1477977650
2013-09-14 03:22:46.043 demo[5174] *(p + 2) : 582339137
2013-09-14 03:22:46.043 demo[5174] *(p + 3) : 1949162477
2013-09-14 03:22:46.043 demo[5174] *(p + 4) : 182130657
2013-09-14 03:22:46.043 demo[5174] *(p + 5) : 1969764839
2013-09-14 03:22:46.043 demo[5174] *(p + 6) : 105257148
2013-09-14 03:22:46.043 demo[5174] *(p + 7) : 2047958726
2013-09-14 03:22:46.043 demo[5174] *(p + 8) : 1728142015
2013-09-14 03:22:46.043 demo[5174] *(p + 9) : 1802605257
Objective_c_arrays.htm