prefer_contains

Always 'false' because 'indexOf' is always greater than or equal to -1.

Always 'true' because 'indexOf' is always greater than or equal to -1.

Unnecessary use of 'indexOf' to test for containment.

The analyzer produces this diagnostic when the method indexOf is used and the result is only compared with -1 or 0 in a way where the semantics are equivalent to using contains.

The following code produces this diagnostic because the condition in the if statement is checking to see whether the list contains the string:

void f(List<String> l, String s) {
  if (l.indexOf(s) < 0) {
    // ...
  }
}

Use contains instead, negating the condition when necessary:

void f(List<String> l, String s) {
  if (l.contains(s)) {
    // ...
  }
}

除非另有说明，文档之所提及适用于 Dart 3.7.3 版本，本页面最后更新时间: 2025-05-08。 查看文档源码 或者 报告页面问题。