What Is a Service in Angular and Why Should You Use it?
Angular Services
Angular services are singleton objects that get instantiated only once during the lifetime of an application. They contain methods that maintain data throughout the life of an application, i.e. data does not get refreshed and is available all the time. The main objective of a service is to organize and share business logic, models, or data and functions with different components of an Angular application.
An example of when to use services would be to transfer data from one controller to another custom service.
Why Should We Use Services in Angular?
The separation of concerns is the main reason why Angular services came into existence. An Angular service is a stateless object and provides some very useful functions. These functions can be invoked from any component of Angular, like Controllers, Directives, etc. This helps in dividing the web application into small, different logical units which can be reused.
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For example, your controller is responsible for the flow of data and binding the model to view. An Angular application can have multiple controllers, to fetch data that is required by the entire application. Making an AJAX call to the server from the controller is redundant, as each controller will use a similar code to make a call for the same data. In such cases, it's extremely useful to use a service, as we can write a service that contains the code to fetch data from the server and inject the service into the controller. Services will have functions to make a call. We can use these functions of services in the controller and make calls to the server, that way we need not write the same code again and it can be used in components other than controllers as well. Also, controllers no longer have to perform the task of fetching the data, as services take care of this, thus achieving the objective of Separation of Concerns.
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