Re: When to instantiate a new class

On 27 June 2015 19:05:18 BST, Larry Garfield <larry@garfieldtech.com> wrote: >On 06/20/2015 08:00 AM, Jesse Schalken wrote: >> Also also, I've never quite figured out why "dependency injection >> containers" exist. Dependency injection just means you pass through >to a >> class/method the things it needs, rather than letting it instantiate >them >> itself, so the caller can decide how those dependencies are >implemented. If >> lots of things need the same set of dependencies, then just wrap them >all >> up in another class that has properties or getters for each. It's not >hard. > >What you describe is a service locator. Which is basically the same >thing as a dependency injection container that you pass into the object > >you're using. Google "service locator bad" for why you shouldn't do >that. :-) > >--Larry Garfield I do think in some circumstances it's the responsibility of the class itself to ensure only one instance of itself exists. Consider a class that loads in file excerpts on a loop, and stores them in the object structure to avoid repetitive disk reads that aren't necessary. If the class is set up as a Singleton, it can't be misused by other code. Dependency injection won't solve that. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.