Select based on enum in Angular2
TypescriptAngularAngular2 FormsTypescript Problem Overview
I have this enum (I'm using TypeScript) :
export enum CountryCodeEnum {
France = 1,
Belgium = 2
}
I would like to build a select in my form, with for each option the enum integer value as value, and the enum text as label, like this :
<select>
<option value="1">France</option>
<option value="2">Belgium</option>
</select>
How can I do this ?
Typescript Solutions
Solution 1 - Typescript
One more solution if you don't want to create a new pipe. You could also extract keys into helper property and use it:
@Component({
selector: 'my-app',
providers: [],
template: `
<div>
<select>
<option *ngFor="let key of keys" [value]="key" [label]="countries[key]"></option>
</select>
</div>
`,
directives: []
})
export class App {
countries = CountryCodeEnum
constructor() {
this.keys = Object.keys(this.countries).filter(k => !isNaN(Number(k)));
}
}
Demo: http://plnkr.co/edit/CMFt6Zl7lLYgnHoKKa4E?p=preview
Edit:
if you need the options as numbers instead of strings:
- replace
[value]
with[ngValue]
- add
.map(Number)
after.filter(...)
Solution 2 - Typescript
update2 simplified by creating an array
@Pipe({name: 'enumToArray'})
export class EnumToArrayPipe implements PipeTransform {
transform(value) : Object {
return Object.keys(value).filter(e => !isNaN(+e)).map(o => { return {index: +o, name: value[o]}});
}
}
@Component({
...
imports: [EnumsToArrayPipe],
template: `<div *ngFor="let item of roles | enumToArray">{{item.index}}: {{item.name}}</div>`
})
class MyComponent {
roles = Role;
}
update
instead of pipes: [KeysPipe]
use
@NgModule({
declarations: [KeysPipe],
exports: [KeysPipe],
}
export class SharedModule{}
@NgModule({
...
imports: [SharedModule],
})
original
Using the keys
pipe from https://stackoverflow.com/a/35536052/217408
I had to modify the pipe a bit to make it work properly with enums (see also https://stackoverflow.com/questions/18111657/how-does-one-get-the-names-of-typescript-enum-entries)
@Pipe({name: 'keys'})
export class KeysPipe implements PipeTransform {
transform(value, args:string[]) : any {
let keys = [];
for (var enumMember in value) {
if (!isNaN(parseInt(enumMember, 10))) {
keys.push({key: enumMember, value: value[enumMember]});
// Uncomment if you want log
// console.log("enum member: ", value[enumMember]);
}
}
return keys;
}
}
@Component({ ...
pipes: [KeysPipe],
template: `
<select>
<option *ngFor="let item of countries | keys" [value]="item.key">{{item.value}}</option>
</select>
`
})
class MyComponent {
countries = CountryCodeEnum;
}
See also https://stackoverflow.com/questions/37046138/how-to-use-ngfor-with-object/37046743#37046743
Solution 3 - Typescript
Here is a very straightforward way for Angular2 v2.0.0. For completeness sake, I have included an example of setting a default value of the country
select via reactive forms.
@Component({
selector: 'my-app',
providers: [],
template: `
<div>
<select id="country" formControlName="country">
<option *ngFor="let key of keys" [value]="key">{{countries[key]}}</option>
</select>
</div>
`,
directives: []
})
export class App {
keys: any[];
countries = CountryCodeEnum;
constructor(private fb: FormBuilder) {
this.keys = Object.keys(this.countries).filter(Number);
this.country = CountryCodeEnum.Belgium; //Default the value
}
}
Solution 4 - Typescript
I've preferred to have a simple utility function shared across my Angular App, to convert the enum
into a standard array to build selects:
export function enumSelector(definition) {
return Object.keys(definition)
.map(key => ({ value: definition[key], title: key }));
}
to fill a variable in the Component with:
public countries = enumSelector(CountryCodeEnum);
and then fill my Material Select as my old array based ones:
<md-select placeholder="Country" [(ngModel)]="country" name="country">
<md-option *ngFor="let c of countries" [value]="c.value">
{{ c.title }}
</md-option>
</md-select>
Thanks for this thread!
Solution 5 - Typescript
Another similar solution, that does not omit "0" (like "Unset"). Using filter(Number) IMHO is not a good approach.
@Component({
selector: 'my-app',
providers: [],
template: `
<select>
<option *ngFor="let key of keys" [value]="key" [label]="countries[key]"></option>
</select>`,
directives: []
})
export class App {
countries = CountryCodeEnum;
constructor() {
this.keys = Object.keys(this.countries).filter(f => !isNaN(Number(f)));
}
}
// ** NOTE: This enum contains 0 index **
export enum CountryCodeEnum {
Unset = 0,
US = 1,
EU = 2
}
Solution 6 - Typescript
Another spin off of this answer, but this actually maps the values as numbers, instead of converting them to strings which is a bug. It also works with 0 based enums
@Component({
selector: 'my-app',
providers: [],
template: `
<select>
<option *ngFor="let key of keys" [value]="key" [label]="countries[key]"></option>
</select>`,
directives: []
})
export class App {
countries = CountryCodeEnum;
constructor() {
this.keys = Object.keys(this.countries)
.filter(f => !isNaN(Number(f)))
.map(k => parseInt(k));;
}
}
Solution 7 - Typescript
As of Angular 6.1 and above you can use the built-in KeyValuePipe
like below (pasted from angular.io docs).
I'm assuming that an enum contains human friendly readable strings of course :)
@Component({
selector: 'keyvalue-pipe',
template: `<span>
<p>Object</p>
<div *ngFor="let item of object | keyvalue">
{{item.key}}:{{item.value}}
</div>
<p>Map</p>
<div *ngFor="let item of map | keyvalue">
{{item.key}}:{{item.value}}
</div>
</span>`
})
export class KeyValuePipeComponent {
object: {[key: number]: string} = {2: 'foo', 1: 'bar'};
map = new Map([[2, 'foo'], [1, 'bar']]);
}
Solution 8 - Typescript
With string enums you can try this.
My string enum has the following definition:
enum StatusEnum {
Published = <any> 'published',
Draft = <any> 'draft'
}
and translates to js in the following way:
{
Published: "published",
published: "Published",
Draft: "draft",
draft: "Draft"
}
I have a few of these in my project so created small helper function in a shared service lib:
@Injectable()
export class UtilsService {
stringEnumToKeyValue(stringEnum) {
const keyValue = [];
const keys = Object.keys(stringEnum).filter((value, index) => {
return !(index % 2);
});
for (const k of keys) {
keyValue.push({key: k, value: stringEnum[k]});
}
return keyValue;
}
}
Init in your component constructor and Bind it to your template like this:
In component:
statusSelect;
constructor(private utils: UtilsService) {
this.statusSelect = this.utils.stringEnumToKeyValue(StatusEnum);
}
In template:
<option *ngFor="let status of statusSelect" [value]="status.value">
{{status.key}}
</option>
Don't forget to add the UtilsService to the provider array in your app.module.ts so you can easily inject it in different components.
I'm a typescript newbie so please correct me if I'm wrong or if there are better solutions.
Solution 9 - Typescript
This is the best option which you can apply without any pipes or extra code.
import { Component } from '@angular/core';
enum AgentStatus {
available =1 ,
busy = 2,
away = 3,
offline = 0
}
@Component({
selector: 'my-app',
template: `
<h1>Choose Value</h1>
<select (change)="parseValue($event.target.value)">
<option>--select--</option>
<option *ngFor="let name of options"
[value]="name">{{name}}</option>
</select>
<h1 [hidden]="myValue == null">
You entered {{AgentStatus[myValue]}}
</h1>`
})
export class AppComponent {
options : string[];
myValue: AgentStatus;
AgentStatus : typeof AgentStatus = AgentStatus;
ngOnInit() {
var x = AgentStatus;
var options = Object.keys(AgentStatus);
this.options = options.slice(options.length / 2);
}
parseValue(value : string) {
this.myValue = AgentStatus[value];
}
}
Solution 10 - Typescript
Yet another Solution with Angular 6.1.10 / Typescript ...
enum Test {
No,
Pipe,
Needed,
Just,
Use,
Filter
}
console.log('Labels: ');
let i = 0;
const selectOptions = [
];
Object.keys(Test).filter(key => !Number(key) && key !== '0').forEach(key => {
selectOptions.push({position: i, text: key});
i++;
});
console.log(selectOptions);
This will print:
Console:
Labels:
(6) [{…}, {…}, {…}, {…}, {…}, {…}]
0: {position: 0, text: "No"}
1: {position: 1, text: "Pipe"}
2: {position: 2, text: "Needed"}
3: {position: 3, text: "Just"}
4: {position: 4, text: "Use"}
5: {position: 5, text: "Filter"}
Solution 11 - Typescript
export enum Unit
{
Kg = 1,
Pack,
Piece,
Litre
}
//with map
import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'enumToArray'
})
export class EnumToArrayPipe implements PipeTransform {
transform(enumObj: Object) {
const keys = Object.keys(enumObj).filter(key => parseInt(key));
let map = new Map<string, string>();
keys.forEach(key => map.set(key, enumObj[key]))
console.log( Array.from(map));
return Array.from(map);
}
}
//With set
import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'enumToArray'
})
export class EnumToArrayPipe implements PipeTransform {
transform(enumObj: Object) {
const keys = Object.keys(enumObj).filter(key => parseInt(key));
let set = new Set();
keys.forEach(key => set.add({ key: parseInt(key), value: enumObj[key] }))
return Array.from(set);
}
}