typescript 如何在打字稿和角度中定义静态常量
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how to define static constants in typescript and angular
提问by Janier
I have bunch of constants which are business related and I have to store them in Angular.Something like below
我有一堆与业务相关的常量，我必须将它们存储在 Angular.Something 中，如下所示
STUDENT_NAMES= ["JOHN","BOB","NICK"]
TEACHER_NAME = ["HARRY","CHRIS"]
SCHOOL_CODE = [100,102,107];
I have a lot of them and they are kind of static ..I need them in most of my service classes. What is the best place to store them? Should i create a interface and let my service class inherit them? In java , we define a class of public static final constants and other classes uses them.Like this , what is the typescript way?
我有很多它们，它们是静态的……我在大多数服务类中都需要它们。存放它们的最佳位置是什么？我应该创建一个接口并让我的服务类继承它们吗？在java中，我们定义了一个public static final常量的类，其他类使用它们。像这样，打字稿的方式是什么？
回答by pzaenger
Define an abstract class for your constants:
为常量定义一个抽象类：
export abstract class Constants {
static readonly STUDENT_NAMES: string[] = ["JOHN", "BOB", "NICK"];
static readonly TEACHER_NAME: string[] = ["HARRY", "CHRIS"];
static readonly SCHOOL_CODE: number[] = [100, 102, 107];
}
Then include this class whereever needed with import { Constants } from '...';and use its values with const names: string[] = Constants.STUDENT_NAMES;
然后在任何需要的地方包含这个类，import { Constants } from '...';并使用它的值const names: string[] = Constants.STUDENT_NAMES;
Regarding the naming I agree with @AdrianBrand to prefer names like studentNames, teacherNamesand schoolCodes.
关于命名我同意@AdrianBrand 更喜欢像studentNames,teacherNames和schoolCodes.
Edit:TypeScript 3.4 introduced so called constassertions, which might also be suited:
编辑：TypeScript 3.4 引入了所谓的constassertions，它也可能适合：
export const constants = {
studentNames: ["JOHN", "BOB", "NICK"],
...
} as const;
回答by Adrian Brand
You put them in a TypeScript file and import them where needed.
你把它们放在一个 TypeScript 文件中，并在需要的地方导入它们。
export const STUDENT_NAMES: string[] = ["JOHN","BOB","NICK"];
Put it in student-names.ts
把它放在 student-names.ts
import { STUDENT_NAMES } from './path/cosnstants/student-names';
where you need it.
你需要的地方。
Personally I would name them studentNames and not STUDENT_NAMES but that is a matter of taste.
就个人而言，我会将它们命名为 studentNames 而不是 STUDENT_NAMES，但这是一个品味问题。
回答by Mohamed Ali RACHID
You can create a TS file constants.tsthat contains all your constants :
您可以创建一个constants.ts包含所有常量的 TS 文件：
export const constants = {
STUDENT_NAMES: ["JOHN","BOB","NICK"],
TEACHER_NAME: ["HARRY","CHRIS"],
SCHOOL_CODE: [100,102,107]
};
Then whenever you need a constant you can call it like this code bellow:
然后，每当您需要一个常量时，您都可以像下面的代码一样调用它：
let studentsNames : any = constants.STUDENT_NAMES;
Regards,
问候，
回答by Rahul
Add all your constants in environment.tsfile - this is the best practice and there will be no change in the values basd on the environment specific
在environment.ts文件中添加所有常量- 这是最佳实践，基于特定环境的值不会发生变化
Add both in environment.tsand environment.prod.ts- this will be your global object and can be accessed at any level
添加environment.ts和environment.prod.ts- 这将是您的全局对象，可以在任何级别访问
Importing will be same as importing an interface or any class Thanks - Happy coding
导入将与导入接口或任何类相同 谢谢 - 快乐编码
回答by Jayampathy Wijesena
you could try enums, this will allow you to define a set of named constants. Refer to this document.
您可以尝试枚举，这将允许您定义一组命名常量。请参阅此文档。
enum Constants {
STUDENT_NAMES= ["JOHN","BOB","NICK"]
TEACHER_NAME = ["HARRY","CHRIS"]
SCHOOL_CODE = [100,102,107];
}
