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context-chain.ts
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context-chain.ts
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// Copyright IBM Corp. 2019. All Rights Reserved.
// Node module: @loopback/example-context
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT
import {Context, inject} from '@loopback/context';
class Greeter {
constructor(@inject('prefix') private prefix: string) {}
greet(name: string) {
return `[${this.prefix}] Hello, ${name}!`;
}
}
export async function main() {
const appCtx = new Context('app');
// Create a context per request, with `appCtx` as the parent
const requestCtx = new Context(appCtx, 'request');
const greeterBinding = appCtx
.bind('services.Greeter')
.toClass(Greeter)
.tag('greeter');
// Set prefix to `app` at app context level
appCtx.bind('prefix').to(appCtx.name);
// Get a greeter from request context
let greeter = await requestCtx.get<Greeter>(greeterBinding.key);
// Inherit `prefix` from app context
console.log(greeter.greet('John'));
// Set `prefix` at request context level
requestCtx.bind('prefix').to(requestCtx.name);
greeter = await requestCtx.get<Greeter>(greeterBinding.key);
// Now the request context prefix is used
console.log(greeter.greet('John'));
// Get a greeter from app context
greeter = await appCtx.get<Greeter>(greeterBinding.key);
// Now the app context prefix is used
console.log(greeter.greet('John'));
}
if (require.main === module) {
main().catch(err => {
console.error(err);
process.exit(1);
});
}