Angular Injectable decorator - Expected 0 arguments but got 1
I also had this problem, and I have resolved it including the name of the class service in "Providers" in app.module.ts.
like this:
@NgModule({
declarations:[
],
imports:[
CommonModule,
HttpClientModule
],
exports:[
],
providers: [
PostListService
]
})
The simplest solution to apply in Angular tutorial is:
1) Remove the unexpected argument in @Injectable decorator (due to your Angular version):
Do not use:
@Injectable({
providedIn: 'root',
})
export class HeroService {
But use:
@Injectable()
export class HeroService {
2) Add HeroService and MessageService to app.module.ts to avoid a No provider for HeroService! execution error due to dependecy injection:
app.module.ts @NgModule metadata:
providers: [
HeroService,
MessageService
],
for angular 5 you need to NOT set the parameter and leave like
@Injectable(/* without any parameter here for angular 5 */)
This is a new feature in Angular 6.
@Injectable({
providedIn: 'root'
})
You have two options:
Refer to the Angular 5 documentation. (As @r-richards notes - change the version of the docs to v5 in the dropdown at the bottom of the left nav.)
Upgrade your project to Angular 6 to fix the issue
Follow the official Angular upgrade guide.
You'll fill out a short form selecting which version of Angular you are on and which version you want to upgrade to. It then shows you the list of necessary steps to take to perform the upgrade. You should follow this guide for all upgrades.
https://update.angular.io/
Here are some notes I took while upgrading from Angular 5 to Angular 6.
Your mileage may vary depending on your configuration. I linked to a couple articles below that helped me.
Update npm (Node Package Manager)
npm install npm@latest -g
Upgarde node
For Windows and mac users, the easiest method is with the official Node installer. Or see the article below for linux/unix.
https://nodejs.org/en/download/
Upgarde Angular CLI globally and locally
npm install -g @angular/cli
npm install @angular/cli
Update package.json
ng update @angular/cli
Update @Angular/Core
ng update @angular/core
Update Angular Material if you're using it
ng update @angular/material
Check for other packages that may need to be upgraded
npm outdated
Update all outdated packages
npm update
Or to upgrade a specific package
npm update <package name>
You may need to convert the angular-cli.json file to angular.json
ng update @angular/cli --migrate-only --from=1.7.4
And as @Sharondio notes, it never hurts to restart your IDE, and possibly your entire computer at this point if you're seeing weirdisms.
References:
Upgrading Node
http://www.hostingadvice.com/how-to/update-node-js-latest-version/
Upgrading Angular
https://vitalflux.com/upgrade-angular-5-app-angular-6/
Other Troubleshooting Steps
https://stackoverflow.com/a/49811824/151325