Utilize the ng.IFilterService interface within a TypeScript project

Question

Utilize the ng.IFilterService interface within a TypeScript project

I am facing an issue with a .ts file that contains the following code:

module App.Filters {
    export class SplitRangeFilter implements ng.IFilterService {
        static $inject = ['$filter'];

        public static factory(): Function {
            return (input: string, splitIndex: number) => {
                return input.split('-')[splitIndex];
            }
        }
    }

    angular.module("App.Filters", []).filter('SplitRange', () => SplitRangeFilter.factory);
}

The compiler is giving me an error message stating:

Class SplitRangeFilter declared interface IFilterService but does not implement it: Types 'SplitRangeFilter' and 'IFilterService' have incompatible signatures. No matching signature for '<T>(name: string) => T'

I have checked the Angular documentation but could not find any information on this signature. Any suggestions on how to resolve this compiler error in VS2015?

javascript angularjs typescript angularjs-filter

Answer 1

Answer №1

Utilizing the IFilterService ensures that programmatic filter calls are type safe when implemented with TypeScript.

To correctly set up your code, follow this implementation:

module App.Filters {
    // Incorporate filter types into the service for TypeScipt to check future programmatic calls.
    export interface IAppFilterService extends angular.IFilterService {
        (name: 'SplitRange'): (input: string | splitIndex: number) => string | undefined;
    }
    export class SplitRangeFilter {
        constructor() {
            return (input: string, splitIndex: number): string | undefined => {
                return input.split('-')[splitIndex];
            }
        }
    }

    angular.module("App.Filters", []).filter('SplitRange', SplitRangeFilter);
}

This is how you'll integrate IAppFilterService in your code:

// Utilization of IAppFilterService
class AppController {
    constructor(private $filter: IAppFilterService) {}

    // Compiles successfully without warnings
    public splitString(val: string, index: number): string | undefined {
        return this.$filter('SplitRange')(val, number);
    }

    // Triggers a compile-time TypeScript error
    public splitNumber(val: number, index: number): string | undefined {
        return this.$filter('SplitRange')(val, number);
    }
}

Answer 2

Utilizing the IFilterService ensures that programmatic filter calls are type safe when implemented with TypeScript.

To correctly set up your code, follow this implementation:

module App.Filters {
    // Incorporate filter types into the service for TypeScipt to check future programmatic calls.
    export interface IAppFilterService extends angular.IFilterService {
        (name: 'SplitRange'): (input: string | splitIndex: number) => string | undefined;
    }
    export class SplitRangeFilter {
        constructor() {
            return (input: string, splitIndex: number): string | undefined => {
                return input.split('-')[splitIndex];
            }
        }
    }

    angular.module("App.Filters", []).filter('SplitRange', SplitRangeFilter);
}

This is how you'll integrate IAppFilterService in your code:

// Utilization of IAppFilterService
class AppController {
    constructor(private $filter: IAppFilterService) {}

    // Compiles successfully without warnings
    public splitString(val: string, index: number): string | undefined {
        return this.$filter('SplitRange')(val, number);
    }

    // Triggers a compile-time TypeScript error
    public splitNumber(val: number, index: number): string | undefined {
        return this.$filter('SplitRange')(val, number);
    }
}

Answer 3

Answer №2

Simply looking for a functioning solution without worrying about adhering to the "correct" interface? Just delete implements ng.IFilterService and update your Angular registration statement to call the factory method (i.e. include ())

angular.module("App.Filters", []).filter('SplitRange', () => SplitRangeFilter.factory());

Answer 4

Simply looking for a functioning solution without worrying about adhering to the "correct" interface? Just delete implements ng.IFilterService and update your Angular registration statement to call the factory method (i.e. include ())

angular.module("App.Filters", []).filter('SplitRange', () => SplitRangeFilter.factory());

Utilize the ng.IFilterService interface within a TypeScript project

Answer №1

Answer №2

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