Return array from a function

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2023-12-01

Objective-C编程语言不允许将整个数组作为参数返回给函数。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。您将在下一章学习指针，这样您就可以跳过本章，直到您理解Objective-C中的指针概念。

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() {
.
.
.
}

要记住的第二点是Objective-C不主张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static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调用此函数如下 -

#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，它产生的结果如下 -

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