The error message "Can't resolve all parameters for CustomerService" is preventing Angular from injecting HttpClient

I have a customerService where I am attempting to inject httpClient. The error occurs on the line where I commented //error happens on this line. Everything works fine until I try to inject httpClient into my service.

The error message is:

`compiler.js:485 Uncaught Error: Can't resolve all parameters for CustomerService: (?).
    at syntaxError (compiler.js:485)
    at CompileMetadataResolver._getDependenciesMetadata (compiler.js:15700)
    at CompileMetadataResolver._getTypeMetadata (compiler.js:15535)
    at CompileMetadataResolver._getInjectableMetadata (compiler.js:15515)
    at CompileMetadataResolver.getProviderMetadata (compiler.js:15875)
    at compiler.js:15786
    at Array.forEach (<anonymous>)
    at CompileMetadataResolver._getProvidersMetadata (compiler.js:15746)
    at CompileMetadataResolver.getNgModuleMetadata (compiler.js:15314)
    at CompileMetadataResolver.getNgModuleSummary

(compiler.js:15133)`

I'm not sure where to begin debugging this. Any help would be greatly appreciated. Thank you!

import { Observable } from "rxjs";
import { Injectable } from "@angular/core";
import { HttpClient } from "@angular/common/http";

@Injectable()
export class CustomerService {

    private baseUri: string = "hosthere.com"

    constructor(
        private http: HttpClient //error happens on this line
    ) { }

    get(email: string): Observable<any> {
        const uri = `${this.baseUri}/customer/${email}`;
        return this.http.get(uri).map(res => res.json());
    }
}

Here is my Customer Module

import { NgModule } from "@angular/core";
import { SharedModule } from "../../shared/shared.module";

import { CustomerRouteModule } from "./cutomer.route.module";

import { SearchComponent } from "./";

import { CustomerService } from "../../services";


    @NgModule({
        imports: [SharedModule, CustomerRouteModule],
        declarations: [SearchComponent],
        providers: [CustomerService],
        exports: []
    })
    export class CustomerModule {

    }

Here is my shared module

import { NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";
import { FormsModule, ReactiveFormsModule } from "@angular/forms";
import { HttpClientModule  } from "@angular/common/http";
import { AppMaterialModule } from "./app.material.module";
import { FlexLayoutModule } from "@angular/flex-layout";

import { HttpClientProvider } from "../services";


@NgModule({
    imports: [
        CommonModule,
        FormsModule,
        ReactiveFormsModule,
        HttpClientModule ,
        AppMaterialModule
    ],
    providers: [

    ],
    exports: [
        AppMaterialModule,
        FlexLayoutModule,
        FormsModule,
        HttpClientModule 
    ]
})
export class SharedModule {

}

Answer №1

It seems like you may have been referencing an outdated guide or tutorial for http protocols.

When utilizing the HttpClient in your code, remember to specify the type of data you expect to receive. This eliminates the need to manually map the data and ultimately streamlines your code.

get(email: string): Observable<any> {
        const uri = `${this.baseUri}/customer/${email}`;
            //add your model here something like 
            //return this.http.get<Customer>(uri);
        return this.http.get<any>(uri);
    }

Keep in mind that if you provide a response type, there is no need to explicitly define a type. Below is a snippet from the official Angular documentation illustrating this concept:

getTextFile(filename: string) {
  // The Observable returned by get() is of type Observable<string>
  // because a text response was specified.
  // There's no need to pass a <string> type parameter to get().
  return this.http.get(filename, {responseType: 'text'})
    .pipe(
      tap( // Log the result or error
        data => this.log(filename, data),
        error => this.logError(filename, error)
      )
    );
}

Answer №2

I discovered the solution right here:

'Uncaught Error: Can't resolve all parameters for' runtime error when upgrading from Angular 4 to 5.0.1

It turns out I had inadvertently removed reflection from my polyfills. Silly mistake on my part.

A big thank you to everyone who provided assistance.

Answer №3

Start by either creating a new file or adding to an existing one called polyfills.ts

import 'core-js/es7/reflect';

Don't forget to include it in your webpack.config file

module.exports = {
    mode: 'production',
    devtool: 'source-map',
    entry: {
        'app': './ClientApp/main.ts',
        'polyfills': './ClientApp/polyfills.ts'
    },...

This step has been really helpful for me

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