How to migrate 0.16 code using Effects.task to equivalent 0.17 code

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Janis Voigtländer

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May 19, 2016, 6:38:18 AM5/19/16
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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

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May 19, 2016, 7:02:48 AM5/19/16
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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

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May 19, 2016, 12:10:13 PM5/19/16
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Janis Voigtländer

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May 19, 2016, 1:02:19 PM5/19/16
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Cool. I've made a pull request streamlining the recommendation a bit, and covering an additional case.

2016-05-19 18:10 GMT+02:00 Frederick Yankowski <fre...@gmail.com>:

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