ngFor 完整列表和唯一列表

Question

抱歉，如果这是一个重复的问题，我是 Angular 的新手，我已经尝试实施多种解决方案但无济于事，而且似乎找不到可以解决我的问题的线索.

我正处于设置网络应用程序的初始阶段，所以现在我正在使用 InMemoryDataService（我确实在 Laravel 中设置了服务，只是还没有绑定它们) 看起来像这样：

import { InMemoryDbService } from 'angular-in-memory-web-api';

export class InMemoryDataService implements InMemoryDbService {
createDb() {
const passwords = [
{ id: 1, team_id: 1, team_name: 'Dragons', fname: 'Bob', lname: 'Smith'},
{ id: 2, team_id: 1, team_name: 'Dragons', fname: 'Jason', lname: 'Roberts'},
{ id: 3, team_id: 1, team_name: 'Dragons', fname: 'Mike', lname: 'Ferraro'},
{ id: 4, team_id: 2, team_name: 'Eagles', fname: 'Jeremy', lname: 'Lovano'},
{ id: 5, team_id: 2, team_name: 'Eagles', fname: 'Robert', lname: 'Casey'},
{ id: 6, team_id: 3, team_name: 'Wolves', fname: 'Mark', lname: 'Thomas'},
{ id: 7, team_id: 3, team_name: 'Wolves', fname: 'Steve', lname: 'Garner'}
];
return {clients};
}
}

我可以让它正常显示并使用 ngFor 构建数据 table 但我还想有一个 select 菜单只使用独特的团队，就像这样：

<select>
<option value="1">Dragons</option>
<option value="2">Eagles</option>
<option value="3">Wolves</option>
</select>

完成此任务的最佳方法是什么？

Answer 1

你可以这样做：

const clients = [
    { id: 1, team_id: 1, team_name: 'Dragons', fname: 'Bob', lname: 'Smith'},
    { id: 2, team_id: 1, team_name: 'Dragons', fname: 'Jason', lname: 'Roberts'},
    { id: 3, team_id: 1, team_name: 'Dragons', fname: 'Mike', lname: 'Ferraro'},
    { id: 4, team_id: 2, team_name: 'Eagles', fname: 'Jeremy', lname: 'Lovano'},
    { id: 5, team_id: 2, team_name: 'Eagles', fname: 'Robert', lname: 'Casey'},
    { id: 6, team_id: 3, team_name: 'Wolves', fname: 'Mark', lname: 'Thomas'},
    { id: 7, team_id: 3, team_name: 'Wolves', fname: 'Steve', lname: 'Garner'}
];

const uniqueTeams = [];

clients.forEach(client => {
   if(unqiueTeams.indexOf(client.team_name) === -1) {
       uniqueTeams.push(client.team_name);
   }
});

console.log(uniqueTeams);

Answer 2

您可以使用 angular 较新版本默认提供的 lodash 库

有 uniqBy 属性删除重复。

例如

let clients = [
    { id: 1, team_id: 1, team_name: 'Dragons', fname: 'Bob', lname: 'Smith'},
    { id: 2, team_id: 1, team_name: 'Dragons', fname: 'Jason', lname: 'Roberts'},
    { id: 3, team_id: 1, team_name: 'Dragons', fname: 'Mike', lname: 'Ferraro'},
    { id: 4, team_id: 2, team_name: 'Eagles', fname: 'Jeremy', lname: 'Lovano'},
    { id: 5, team_id: 2, team_name: 'Eagles', fname: 'Robert', lname: 'Casey'},
    { id: 6, team_id: 3, team_name: 'Wolves', fname: 'Mark', lname: 'Thomas'},
    { id: 7, team_id: 3, team_name: 'Wolves', fname: 'Steve', lname: 'Garner'}
];

clients = _.uniqBy(clients, 'team_name');
console.log(clients);

Answer 3

为此您不需要 lodash，管道也不是一个好主意（参见 https://angular.io/guide/pipes#no-filter-pipe）。

使用一些现代的方法简单地创建一个独特的元素列表 Javascript:

this.uniqueTeams = Array.from(new Set(teams.map(team => team.team_name)));

这是类型安全的、无依赖性的并且没有性能问题。

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