Angular提供程序必须从$ get工厂方法返回一个值

Question

So I have a problem with my angular factory that I've been trying to solve for a while now. I guess my knowledge in angular isn't quite enough here.

Most of the code I will post here is reused code from another part of the solution that I didn't write. So that's probably the reason why I can't figure this out. Also this is the first ever factory I've made.

(function () {
'use strict';

angular.module('app.coordinate-transformer-service', [])
    .factory('coordinateTransformerService', coordinateTransformerService);

coordinateTransformerService.$inject = ['proj4js', 'gmaps'];

function coordinateTransformerService(proj4js, gmaps, objectsEpsgCode) {

    var factory = {};

    factory.$get = ['proj4js', function coordinateTransformerFactory(proj4js) {
        return new coordinateTransformerService(proj4js, gmaps, objectsEpsgCode);
    }];

    var mapProjection = 'EPSG:4326', // WGS84 latlong
            objectsProjection = 'EPSG:' + objectsEpsgCode,
            transformCoordinatesToLatLng = function (point) {
                if (objectsProjection === mapProjection) {
                    return new gmaps.LatLng(point.y, point.x);
                }

                var newPoint = {
                    x: point.x,
                    y: point.y
                };
                proj4js.transform(new proj4js.Proj(objectsProjection), new proj4js.Proj(mapProjection), newPoint);
                return new gmaps.LatLng(newPoint.y, newPoint.x);
            };

    factory.transformLatLngToProject = function (latlng) {
        if (!factory.isFunction(latlng.lng) || !factory.isFunction(latlng.lat)) {
            throw new Error("No functions lat() or lng() exists on parameter latlng");
        }

        var newPoint = {
            x: latlng.lng(),
            y: latlng.lat()
        };

        proj4js.transform(new proj4js.Proj(mapProjection), new proj4js.Proj(objectsProjection), newPoint);
        newPoint = roundPointsToCorrectDecimals(newPoint);

        return newPoint;
    };

    factory.roundPointsToCorrectDecimals = function (point) {
        var noDecimals = objectsEpsgCode === 4326 ? 5 : 0;

        if (!point || !point.x || !point.y) {
            throw new Error("Point, x or y is null or not defined");
        }

        return {
            x: point.x.toFixed(noDecimals),
            y: point.y.toFixed(noDecimals)
        };
    };

    factory.isFunction = function (functionToCheck) {
        var getType = {};
        return functionToCheck && getType.toString.call(functionToCheck) === '[object Function]';
    };

    return factory;
};

//coordinateTransformerService.prototype = {
//    constructor: coordinateTransformerService
//};
//return coordinateTransformerService;
})();

I get the error "Provider 'proj4js' must return a value from $get factory method." And to be honest I don't know what the factory.$get function I have does. That is part of the code I didn't write. Proj4js is a library that convert coordinates from one system to another. So we load objects in from the server to display them on a google map, and some of that don't use latitude longitude. So that is why we need to transform them with proj4js. If that info would help anyone.

But I know a factory method needs to return an object. But am I not doing that already? Maybe it is that factory.$get function that is the problem, as I've said I don't know the purpose of it... But removing it doesn't help^^

Also, don't mind that it's called coodinateTransformerService and not coordinateTransformerFactory. I used a service first, just didn't care to rename it until I got it to work.

EDIT: This may help. In angular.js where the error is thrown:

function enforceReturnValue(name, factory) {
return function enforcedReturnValue() {
  var result = instanceInjector.invoke(factory, this, undefined, name);
  if (isUndefined(result)) {
    throw $injectorMinErr('undef', "Provider '{0}' must return a value from $get factory method.", name);
  }
  return result;
};
}

result gets undefined. Name is proj4js and factory is this which a colleague made:

(function () {
'use strict';

angular.module('blocks.proj4js').factory('proj4js', proj4jsFactory);

proj4jsFactory.$inject = ['$window'];
function proj4jsFactory($window) {
    return $window.proj4js;
}
})();

Answer 1

As I see you mixed up the service and provider. The easiest way to meet your needs will be:

angular.module('app.coordinate-transformer-service', [])
    .service('coordinateTransformerService', CoordinateTransformerService);

CoordinateTransformerService.$inject = ['proj4js', 'gmaps', 'objectsEpsgCode'];

function CoordinateTransformerService(proj4js, gmaps, objectsEpsgCode) {

    var mapProjection = 'EPSG:4326', // WGS84 latlong
            objectsProjection = 'EPSG:' + objectsEpsgCode,
            transformCoordinatesToLatLng = function (point) {
                if (objectsProjection === mapProjection) {
                    return new gmaps.LatLng(point.y, point.x);
                }

                var newPoint = {
                    x: point.x,
                    y: point.y
                };
                proj4js.transform(new proj4js.Proj(objectsProjection), new proj4js.Proj(mapProjection), newPoint);
                return new gmaps.LatLng(newPoint.y, newPoint.x);
            };

    this.transformLatLngToProject = function (latlng) {
        if (!this.isFunction(latlng.lng) || !this.isFunction(latlng.lat)) {
            throw new Error("No functions lat() or lng() exists on parameter latlng");
        }

        var newPoint = {
            x: latlng.lng(),
            y: latlng.lat()
        };

        proj4js.transform(new proj4js.Proj(mapProjection), new proj4js.Proj(objectsProjection), newPoint);
        newPoint = roundPointsToCorrectDecimals(newPoint);

        return newPoint;
    };

    this.roundPointsToCorrectDecimals = function (point) {
        var noDecimals = objectsEpsgCode === 4326 ? 5 : 0;

        if (!point || !point.x || !point.y) {
            throw new Error("Point, x or y is null or not defined");
        }

        return {
            x: point.x.toFixed(noDecimals),
            y: point.y.toFixed(noDecimals)
        };
    };

    this.isFunction = function (functionToCheck) {
        var getType = {};
        return functionToCheck && getType.toString.call(functionToCheck) === '[object Function]';
    };
};