string 如何在 Dart 中对字符串列表进行排序？
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How can I sort a list of strings in Dart?
提问by george koller
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.
我在 API 文档中看到在 上有一个sort()方法List，但我不清楚它需要什么参数。当前需要进行非常简单的直接 alpha 比较。
回答by Seth Ladd
Thanks for the question! You can sort a list of Strings like this:
感谢提问！您可以像这样对字符串列表进行排序：
main() {
var fruits = ['bananas', 'apples', 'oranges'];
fruits.sort();
print(fruits);
}
The above code prints:
上面的代码打印：
apples, bananas, oranges
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:
请注意，sort()它不返回值。它在不创建新列表的情况下对列表进行排序。如果要在同一行中排序和打印，可以使用方法级联：
print(fruits..sort());
For more control, you can define your own comparison logic. Here is an example of sorting the fruits based on price.
如需更多控制，您可以定义自己的比较逻辑。这是根据价格对水果进行分类的示例。
main() {
var fruits = ['bananas', 'apples', 'oranges'];
fruits.sort((a, b) => getPrice(a).compareTo(getPrice(b)));
print(fruits);
}
Let's see what's going on here.
让我们看看这里发生了什么。
A List has a sortmethod, which has one optionalparameter: a Comparator. A Comparator is a typedefor function alias. In this case, it's an alias for a function that looks like:
List 有一个sort方法，它有一个可选参数：Comparator。Comparator 是一个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：
int Comparator(T a, T b)
From the docs:
从文档：
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.
Comparator 函数通过在 a 小于 b 时返回负整数，如果 a 等于 b 返回零，如果 a 大于 b 返回正整数来表示这样的总排序。
回答by Paras khandelwal
Here is the one line code to achieve it.
这是实现它的一行代码。
fruits.sort((String a, String b)=>a.compareTo(b)); //fruits is of type List<String>
回答by JONNALAGADDA Srinivas
To add just one point to Seth's detailed answer, in general, in
仅在赛斯的详细答案中添加一点，一般来说，在
(a, b) => foo(a, b)
passed into sort, the function fooshould answer an integer result as follows:
传入sort，该函数foo应按如下方式回答整数结果：
- if a < b, result should be < 0,
- if a = b, result should be = 0, and
- if a > b, result should be > 0.
- 如果 a < b，结果应该 < 0，
- 如果 a = b，结果应该是 = 0，并且
- 如果 a > b，结果应该 > 0。
For the above law of trichotomy to hold, both aand bmust be Comparables.
对于三分法的上述法律持有，两者a并b必须Comparable秒。
回答by Lasse Nielsen
After today, you should just be able to do list.sort() . The sort method's argument is now optional, and it defaults to a function that calls compareTo on the elements themselves. Since String is Comparable, it should Just Work now.
今天之后，你应该能够执行 list.sort() 。sort 方法的参数现在是可选的，它默认为一个对元素本身调用 compareTo 的函数。由于 String 是 Comparable，它应该立即工作。
