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芦苇花开2023-09-16 16:23

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Dart 基础语法

List数组操作

firstWhere 方法

Dart 官网示例

复制代码

void main() {
  const items = ['Salad', 'Popcorn', 'Toast', 'Lasagne'];

  // You can find with a simple expression:
  var foundItem1 = items.firstWhere((item) => item.length > 5);
  print(foundItem1);

  // Or try using a function block:
  var foundItem2 = items.firstWhere((item) {
    return item.length > 5;
  });
  print(foundItem2);

  // Or even pass in a function reference:
  var foundItem3 = items.firstWhere(predicate);
  print(foundItem3);

  // You can also use an `orElse` function in case no value is found!
  var foundItem4 = items.firstWhere(
    (item) => item.length > 10,
    orElse: () => 'None!',
  );

every、 any方法

复制代码

void main() {
  const items = ['Salad', 'Popcorn', 'Toast'];

  if (items.any((item) => item.contains('a'))) {
    print('At least one item contains "a"');
  }

  if (items.every((item) => item.length >= 5)) {
    print('All items have length >= 5');
  }
}