Objective-C - 改变NSMutableArray的特定元素

NSMutableArray修改元素, 使用-insertObject: atIndex: 和-replaceObjectAtIndex: withObject: 都可以, 即通过插入(insert)和替换(replace)可以实现.
示例:

// 减少按钮监听- (void) onSubBtnPressed:(UIButton*) sender {    NIDPRINTMETHODNAME();    NSInteger times = [[_serviceNumList objectAtIndex:_servicePos] integerValue];    if (times <= 1) {        return;    }    times--; // 减少    // 改变数组数据    [_serviceNumList replaceObjectAtIndex:_servicePos withObject:[NSNumber numberWithInteger:times]];    // 设置数据    UITextField *mo = [_timesFieldArray objectAtIndex:_servicePos];    NSAttributedString* timesText =[[NSAttributedString alloc] initWithString:[NSString stringWithFormat:@"%ld", (long)[[_serviceNumList objectAtIndex:_servicePos] integerValue]]]; // 设置文字    [mo setAttributedText:timesText];    _totalPrice = (float)([_goodsList[_servicePos][@"Price"] floatValue]/100.0)*[[_serviceNumList objectAtIndex:_servicePos] integerValue];    [_totalPriceLabel setText:[NSString stringWithFormat:@"%0.1f", _totalPrice]];}

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