TypeScript + Angular: No index signature with a parameter of type 'string' was found

Question

I have a component that takes information from a service, and I would like to use a forEach statement to initialize component's properties. This does not work:

const variables = ['records' ,'observableComplete' ]
variables.forEach(variable => {
  this.user2RoleService[variable].subscribe( result => { this[variable] = result})
});

But this does work (but I should do it one by one)

const variable = 'observableComplete'
this.user2RoleService[variable].subscribe( result => { this[variable] = result})

Any thoughts how to solve it?

What are you doing with the updated data? Is it being displayed in the template? — wlf
– wlf, Commented Sep 4, 2022 at 5:19
Yes: the updated information is used to reflect changes on the HTML. User2Role2Service basically has a get method to be called, among others. — John G.
– John G., Commented Sep 4, 2022 at 22:46

Arman Ashoori · Accepted Answer · 2022-09-04 05:49:21Z

1

you should use this() instead of [].

const variables = ['records' ,'observableComplete' ]
variables.forEach(variable => {
  this.user2RoleService(variable).subscribe( result => { this[variable] =result})
});

answered Sep 4, 2022 at 5:49

Arman Ashoori

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1 Comment

John G. Over a year ago

Don't work like this. I would like to reference to a class property. The return message with your proposal is: 'This expression is not callable.'

mbojko · Accepted Answer · 2022-09-05 12:27:05Z

0

I'm assuming your user2RoleService is an instance of a class User2RoleService. Therefore, this type declaration should do:

const variables: (keyof User2RoleService)[] = ['records', 'observableComplete'];

answered Sep 5, 2022 at 12:27

mbojko

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Comments

Eliseo · Accepted Answer · 2022-09-05 13:45:13Z

0

I'm afraid that in strict mode you need an "ugly hack"

const variables = ['records', 'observableComplete'];

const self=this as any  //<--this is the uggly hack

variables.forEach((variable: string) => {
  self.user2RoleService[variable].subscribe((result: any) => {
    self[variable]=result;
    console.log(this.records,this.observableComplete) //<--only for check
  });
});

answered Sep 5, 2022 at 13:45

Eliseo

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Comments

Andrei · Accepted Answer · 2022-09-05 13:50:34Z

0

the way you are doing the assignment typescript infers it as string[], however you can improve it with the help of as const. simply do

const variables = ['records' ,'observableComplete' ] as const;

and then the type of variables will be the same tuple provided

answered Sep 5, 2022 at 13:50

Andrei

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