Chaining thunks

[olejnjak]

Hi,

I was wondering whether there is a recommended way how to chain thunks? The original redux-thunk works with promises while our Thunk is just a Void closure which makes chaining a bit complicated.

Thanks in advance.

[mjarvis]

Please note the code below is pseudocode and has not been tested with a compiler.

You can easily wrap this Thunk library with a promise of some kind if you wish to use that method

let promise = Promise()
let thunk = Thunk<MyState> { dispatch, getState in 
    if getState!.loading {
        promise.reject()
        return
    }
    dispatch(RequestStart())
    api.getSomething() { something in
        if something != nil {
            dispatch(RequestSuccess(something))
            promise.fulfill()
        } else {
            dispatch(RequestError())
            promise.reject()
        }
    }
}
store.dispatch(thunk)
promise.then { ... }

You could also write a helper function that creates a thunk with a promise and returns it via a tuple

func foo(...) -> (Thunk<MyState>, promise) { ... }
let (thunk, promise) = foo(...)
store.dispatch(thunk)
promise.then { ... }

If we want to go even further, If you wanted the full behaviour of redux-thunk with dispatch able to return promises, you could extend Store to return promises when a certain type of action is passed in.

struct PromisedThunk<State>: PromisedThunk {
    let promise: Promise
    let thunk: Thunk<State>
    // ...
}
extension Store {
   func dispatch(_ thunk: PromisedThunk) -> Promise {
        dispatch(thunk.thunk)
        return thunk.promise
    }
}

[olejnjak]

Looks OK, will try something, thanks

[Prateekkotian]

How to chain 2 API calls asynchronous by using thunk ? I tried using Promise but it's not available on Reswift