什么是??在达特

问题描述

限时删除！！

在Flutter插件的共享首选项示例中，我看到了该运算符.而且我不明白.

I saw this operator in Example of Shared Preferences for Flutter plugin. And I didn't get it.

int counter = (prefs.getInt('counter') ?? 0) + 1;

推荐答案

它称为空感知运算符

意思是，当且仅当 prefs.getInt('counter')返回 null 时，为其分配 0 ，然后加1.

Meaning, if and only if prefs.getInt('counter') returns null assign 0 to it and then increment by one.

在这里，您可以找到有关空感知运算符的精彩博客文章: http://blog.sethladd.com/2015/07/null-aware-operators-in-dart.html

Here, you can find a great blog post about null-aware operator: http://blog.sethladd.com/2015/07/null-aware-operators-in-dart.html

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