如何在Dart中对字符串列表进行排序? [英] How can I sort a list of strings in Dart?

问题描述

我在API文档中看到List上有一个sort()方法，但是我不清楚参数需要什么.当前的需求是非常简单的向上Alpha比较.

I see in the API docs there is a sort() method on List, but I'm not clear what it needs for a parameter. The current need is for a very simple straight up alpha comparison.

推荐答案

感谢您提出问题！您可以像这样对字符串列表进行排序:

Thanks for the question! You can sort a list of Strings like this:

main() {
  var fruits = ['bananas', 'apples', 'oranges'];
  fruits.sort();
  print(fruits);
}

上面的代码打印:

apples, bananas, oranges

请注意，sort()不返回值.它对列表进行排序而不创建新列表.如果要在同一行中排序和打印，可以使用方法级联:

Notice that sort() does not return a value. It sorts the list without creating a new list. If you want to sort and print in the same line, you can use method cascades:

print(fruits..sort());

要获得更多控制，您可以定义自己的比较逻辑.这是一个根据价格对水果进行排序的示例.

For more control, you can define your own comparison logic. Here is an example of sorting the fruits based on price.

main() {
  var fruits = ['bananas', 'apples', 'oranges'];
  fruits.sort((a, b) => getPrice(a).compareTo(getPrice(b)));
  print(fruits);
}

让我们看看这里发生了什么.

Let's see what's going on here.

列表具有 sort 方法，该方法具有一个可选参数:比较器.比较器是typedef或函数别名.在这种情况下，它是一个函数的别名，如下所示:

A List has a sort method, which has one optional parameter: a Comparator. A Comparator is a typedef or function alias. In this case, it's an alias for a function that looks like:

int Comparator(T a, T b)

从文档中

Comparator函数通过返回a来表示这样的总排序 如果a小于b，则为负整数；如果a等于b，则为零；并且 如果a大于b，则为正整数.

A Comparator function represents such a total ordering by returning a negative integer if a is smaller than b, zero if a is equal to b, and a positive integer if a is greater than b.

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