Objective-C insertObject:atIndex 和 arrayWithCapacity:

这份代码有几处错误？

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"Hello, World!");
        NSMutableArray *array = [NSMutableArray arrayWithCapacity:10];
        //
        [array insertObject:@"234" atIndex:0];
        //
        [array insertObject:@"234" atIndex:5];
        //
        [array replaceObjectAtIndex:7 withObject:@"123"];
    }
    return 0;
}

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"Hello, World!");
        NSMutableArray *array = [NSMutableArray arrayWithCapacity:10];
        //
        [array insertObject:@"234" atIndex:0];
        //错
        [array insertObject:@"234" atIndex:5];
        //错
        [array replaceObjectAtIndex:7 withObject:@"123"];
    }
    return 0;
}

为什么???
看看苹果怎么说

顺便提一下,arrayWithCapacity:这个方法主要是为了提高程序的运行速度.
这是我的独立博客
https://junyixie.github.io/2017/01/16/Objective-C-insertObject-atIndex-%E5%92%8C-arrayWithCapacity/