How to use patchState vs setState in NGXS?

Question

I am learning ngxs but I can't understand when should I use patchState and setState? What's the difference?

const state = ctx.getState();
let data =  this.service.list();
ctx.setState({
    ...state,
    feedAnimals: data
});

vs.

let data =  this.service.list();
ctx.patchState({
    feedAnimals: data
});

Answer 1

Those two pieces of code are equivalent. patchState is just a short hand version of the setState({...state, ... } code.

In future patchState will most likely be evolving to a more useful immutability helper with equality testing (ie. the state would only be changed if the patch actually changes any values) and patch operators (this is still in discussion).

I would recommend using patchState for neatness and to take advantage of features that are on their way.