39 lines
1.1 KiB
Elm
39 lines
1.1 KiB
Elm
module Email exposing (Email, decoder, encode, toString)
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import Json.Decode as Decode exposing (Decoder)
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import Json.Encode as Encode exposing (Value)
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{-| An email address.
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Having this as a custom type that's separate from String makes certain
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mistakes impossible. Consider this function:
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updateEmailAddress : Email -> String -> Http.Request
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updateEmailAddress email password = ...
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(The server needs your password to confirm that you should be allowed
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to update the email address.)
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Because Email is not a type alias for String, but is instead a separate
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custom type, it is now impossible to mix up the argument order of the
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email and the password. If we do, it won't compile!
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If Email were instead defined as `type alias Email = String`, we could
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call updateEmailAddress password email and it would compile (and never
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work properly).
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This way, we make it impossible for a bug like that to compile!
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-}
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type Email
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= Email String
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toString : Email -> String
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toString (Email str) =
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str
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encode : Email -> Value
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encode (Email str) =
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Encode.string str
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decoder : Decoder Email
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decoder =
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Decode.map Email Decode.string
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