Cyclic dependency issue in Angular2

Question

I developed a custom error handler which implements Angular2 Error Handler class. My custom error handler uses a logger service to log errors. The code looks like as follows:

export class CustomErrorHandler implements ErrorHandler {
    constructor(private logger: LoggerService) {}

    handleError(error: any): void {
        logger.error('....');
    }
}

However, since the logger service uses Angular2 router, I cannot inject the logger service to the custom error handler! Running the above code throws the following exception! Error: Provider parse errors:↵Cannot instantiate cyclic dependency!

Why does logger service use router? there are no routes involved with service. Services are supposed to be singletons. — Eddie Martinez
– Eddie Martinez, Commented Mar 2, 2017 at 23:45
It's because our logger service uses a remote logger to send logs to another online service. — Mohammad
– Mohammad, Commented Mar 6, 2017 at 17:27

Kalamarico · Accepted Answer · 2018-04-15 18:03:59Z

1

You need to inject manually, to avoid the cyclic dependency problem because this class is created before the providers, your code should be:

import { Injectable, Injector } from '@angular/core';
import { Logger } from '...';

@Injectable()
export class CustomErrorHandler implements ErrorHandler {
    constructor(private injector: Injector) {}

    handleError(error: any): void {
        const logger = this.injector.get(Logger);
        logger.error('....');
    }
}

edited Apr 15, 2018 at 18:03

answered Jan 26, 2018 at 13:32

Kalamarico

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