How to migrate 0.16 code using Effects.task to equivalent 0.17 code
Janis Voigtländer
Questions how to do migrate 0.16 code involving Effects.task to 0.17 have come up repeatedly now, so I thought it makes sense to write down general advice about this. Below is my advice. In each of the cases below, I first give a snippet of 0.16 code and what I advise to use as equivalent 0.17 code. In each case, when the 0.16 version has some type of the form Effects SomeType, the 0.17 code I give has type Cmd SomeType (for the same SomeType, of course).
So, here goes:
If in 0.16 you had:
task |> Task.toMaybe |> Effects.task
use the following in 0.17:
task |> Task.perform (always Nothing) Just
If in 0.16 you had:
task |> Task.toMaybe |> Task.map action |> Effects.task
use the following in 0.17:
task |> Task.toMaybe |> Task.perform never action
If in 0.16 you had:
task |> Task.toResult |> Effects.task
use the following in 0.17:
task |> Task.perform Err Ok
If in 0.16 you had:
task |> Task.toResult |> Task.map action |> Effects.task
use the following in 0.17:
task |> Task.toResult |> Task.perform never action
The function never used in two places above is from http://package.elm-lang.org/packages/elm-community/basics-extra.
Janis Voigtländer
Oh, and of course, if task was something not involving Task.toMaybe or Task.toResult (for, example, task could have been simply Task.succeed ...), then:
If in 0.16 you had:
task |> Effects.task
use the following in 0.17:
task |> Task.perform never identity
Frederick Yankowski
Janis Voigtländer
I added that info to the FAQ.
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