如何创建二维数组，大小在objective-c中作为变量给出答案

【问题标题】：How to create 2D array and the size is given as a variable in objective-c如何创建二维数组，大小在objective-c中作为变量给出
【发布时间】：2015-11-14 11:24:43
【问题描述】：

我是 Objective-c 的新手。我在二维数组中遇到了麻烦。因为我有一些javascript知识。我会尝试用javascript解释它。

var row = 10;
var col = 10;
var array[row][col];

for (var i = 0; i < row; i++){
    for (var j = 0; j < col; j++){
        //do something in here
    }
}

row = 20;
col = 20;

for (var i = 0; i < row; i++){
    for (var j = 0; j < col; j++){
        //do something in here
    }
}

如何在 Objective-c 中编写代码？

【问题讨论】：

在 ECMAScript 中，var array[row][col] 是一个语法错误。
在目标 c 中，您在声明变量时不指定数组的大小。您只需分配一个 NSMutableArray 并将 NSMutableArrays 添加到其中。
我想我和java混在一起了...

标签： javascript ios objective-c xcode

【解决方案1】：

希望这会有所帮助：

NSInteger row = 10;
NSInteger col = 10;

// Array with variable size. For fixed size, use [[NSMutableArray alloc] initWithCapacity:row]
NSMutableArray* array = [NSMutableArray new];

for (NSInteger i = 0; i < row; i++) {

    // You must add values before you can access them. You cannot access a value at an index which is greater than the size of the array

    NSMutableArray* colArray = [NSMutableArray new];
    [array addObject:colArray];

    for (NSInteger j = 0; j < col; j++) {


        [colArray addObject:someObject];

        // You can access the array like such:
        id object = array[i][j];

        // You can change an existing value in the array using the same notation:
        array[i][j] = someObject;

        // You cannot set an array value to nil or null. Instead use NSNull which is an object you can use to represent a null value:
        array[i][j] = [NSNull null];
    }
}


// You can also initialise an array with the following notation if you know the values in advance:

NSArray* anotherArray = @[objectOne, objectTwo, objectThree];

// Similarly, you can create a 2-dimensional array as follows:

NSArray* twoDimensionalArray = @[
                                 @[rowOneColumnOne, rowOneColumnTwo, rowOneColumnThree],
                                 @[rowTwoColumnOne, rowTwoColumnTwo, rowTwoColumnThree]
                                 ];

【讨论】：