I'm fairly new to Ionic and Angular and I've been reading that working with the dependency injection design pattern is recommended. Now I'm fairly new to DI as well so this is a double whammy for me.
If I have a controller for example:
app.controller('myController', ['$scope', '$localstorage', 'myService'
function($scope, $localstorage, myService) {
// Calls function in service
myService.concatStrings();
}
And I have a service:
app.service('myService', ['$localstorage', function ($localstorage) {
// Reads strings from local storage and concatenates them
function concatStrings () {
// ...
}
}
And say I can read the two strings from local storage like this:
var string1 = $localstorage.getStringOne();
var string2 = $localstorage.getStringTwo();
Where is the recommended place where I get these strings? Do I get them in my controller from $localstorage and pass them to the service, or do I not pass anything to the service and obtain the strings from $localstorage in the service?
I'm of the opinion that I actually read the strings from $localstorage in the controller and then pass it to the service. This way I can easily write unit tests for my services... But I'm not sure :\
you can read the strings from service's only it is recommended because we are going to inject the service as dependency to controller but not vice-versa and you can use $window.localStorage for storing the string values
Services are best used as reusable blocks of self contained code. I would think a concatStrings() method should be given strings to concatenate. If the method is to be concatStringsFromLocalStorage(), then perhaps it should be given some identifier to retrieve the strings from the storage, like perhaps a key or list of keys. The code which then uses localStorage (the service) can know about it, while the calling code (the controller) doesn't have to dirty itself with that knowledge.
The more you can easily reuse your code the more mileage you can get from it. Angular's DI, when used correctly, typically makes writing good tests with separate concerns quite easy.