无法在DART中的地图列表中使用indexOf [英] Can't use indexOf in List of Map in DART

问题描述

我有一个这样的地图列表

I have a List of Map like this

List<Map<String, String>> data = [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  var index = data.indexOf({"id":"1", "name":"Job"});
  print("Index: $index");
}

在DartPad上运行的结果是:索引:-1.如何在列表中的Map对象中使用indexOf?谢谢

Result run on DartPad was: Index: -1. How can I using indexOf for Map object in List? Thanks

推荐答案

它不起作用，因为两个映射不是同一对象，要解决此问题，您可以使用const对象或使用 indexWhere

It doesn't work because the two maps aren't the same Object, to solve that, you can either use const objects or use indexWhere

使用const:

// Create a const (immutable) list.
List<Map<String, String>> data = const [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  // Search for the map.
  var index = data.indexOf(const {"id":"1", "name":"Job"});
  print("Index: $index");
}

使用索引位置:

List<Map<String, String>> data = const [
  {"id":"1", "name":"Job"},
  {"id":"2", "name":"Teh"},
  {"id":"3", "name":"Maru"},
  {"id":"4", "name":"Pam"},
];

void main() {
  // Index where id is 1 and name is Job.
  var index = data.indexWhere((e) => e["id"] == "1" && e["name"] == "Job");
  print("Index: $index");
}

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