Hi all
Just started to play around with elm and very eager to get more fluid. I
picked a silly POC scenario of a rule composer: basically you have regex
rules and want to edit/test them in a form. When applying a regex and
showing the replace output in an input field, I face an "undefined". Below
you see the isolated part forcing my observation while applying the rule
directly in init.
Unfortunately I could really not trace down to the root of this happening.
Is somebody able to tell me:
- What I am doing wrong? Why does there an "undefined" appear? (wenn
executing my own "replace" function in the REPL it works fine as expected)
- How do you guys debug such behaviour?
Here my silly example:
module RuleTest exposing (..)
import Html.App
import Html exposing (..)
import Html.Attributes exposing (..)
import Regex
main : Platform.Program Basics.Never
main =
Html.App.program
{ init = init
, view = viewRuleTest
, update = update
, subscriptions = \_ -> Sub.none
}
type alias Rule =
{ regex : String
, substitution : String
}
type alias RuleTest =
{ rule : Rule
, input : String
, output : String
, matched : Bool
}
type Msg
= StartTest String
-- init
init : (RuleTest, Cmd Msg)
init =
( apply "reg1" (Rule "reg1" "sub1")
, Cmd.none
)
-- update
update : Msg -> RuleTest -> (RuleTest, Cmd Msg)
update msg ruleTest =
case msg of
StartTest input ->
( apply input ruleTest.rule, Cmd.none )
apply : String -> Rule -> RuleTest
apply input rule =
let
output = replace rule.regex rule.substitute input
matched = input /= output
rule = rule
in
RuleTest rule input output True
replace : String -> String -> String -> String
replace regex substitute input =
Regex.replace Regex.All (Regex.regex regex) (\_ -> substitute) input
viewRuleTest : RuleTest -> Html Msg
viewRuleTest ruleTest =
div []
[ label [] [ text "Pattern" ]
, input [ Html.Attributes.value ruleTest.rule.regex, disabled True ] []
, label [] [ text "Substitution" ]
, input [ Html.Attributes.value ruleTest.rule.substitution, disabled
True ] []
, label [] [ text "Input" ]
, input [ Html.Attributes.value ruleTest.input, disabled True ] []
, label [] [ text "Output" ]
, input [ Html.Attributes.value ruleTest.output, disabled True ] []
, label [] [ text "matched" ]
, input [ type' "checkbox", checked ruleTest.matched ] []
]
Environment:
elm repl --version
0.17.1
OSX 10.11.3
{
"version": "1.0.0",
"summary": "helpful summary of your project, less than 80 characters",
"repository": "https://github.com/user/project.git";,
"license": "BSD3",
"source-directories": [
"."
],
"exposed-modules": [],
"dependencies": {
"elm-lang/core": "4.0.1 <= v < 5.0.0",
"elm-lang/html": "1.1.0 <= v < 2.0.0"
},
"elm-version": "0.17.1 <= v < 0.18.0"
}
Thanks for any advice!
Best, Andi
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