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Swap part1 and part2

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This commit is contained in:
Richard Feldman
2018-08-13 05:04:35 -04:00
parent 353623f108
commit 493b5681d4
16 changed files with 156 additions and 156 deletions
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2
advanced/part1/README.md
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@@ -10,4 +10,4 @@ Then open [http://localhost:3000](http://localhost:3000) in your browser.
## Exercise
Open `src/Article.elm` in your editor and resolve the TODOs there.
Open `src/Viewer/Cred.elm` in your editor and resolve the TODOs there.

81
advanced/part1/src/Article.elm
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@@ -56,22 +56,64 @@ import Viewer.Cred as Cred exposing (Cred)
-- TYPES
{-| An article, optionally with an article body.
To see the difference between { extraInfo : a } and { extraInfo : Maybe Body },
consider the difference between the "view individual article" page (which
renders one article, including its body) and the "article feed" -
which displays multiple articles, but without bodies.
This definition for `Article` means we can write:
viewArticle : Article Full -> Html msg
viewFeed : List (Article Preview) -> Html msg
This indicates that `viewArticle` requires an article _with a `body` present_,
wereas `viewFeed` accepts articles with no bodies. (We could also have written
it as `List (Article a)` to specify that feeds can accept either articles that
have `body` present or not. Either work, given that feeds do not attempt to
read the `body` field from articles.)
This is an important distinction, because in Request.Article, the `feed`
function produces `List (Article Preview)` because the API does not return bodies.
Those articles are useful to the feed, but not to the individual article view.
-}
type Article a
= Article Internals a
{-| Metadata about the article - its title, description, and so on.
-- 💡 HINT: We can use these `Preview` and/or `Full` types to store information...
Importantly, this module's public API exposes a way to read this metadata, but
not to alter it. This is read-only information!
If we find ourselves using any particular piece of metadata often,
for example `title`, we could expose a convenience function like this:
type Preview
= Preview
Article.title : Article a -> String
If you like, it's totally reasonable to expose a function like that for every one
of these fields!
type Full
= Full
(Okay, to be completely honest, exposing one function per field is how I prefer
to do it, and that's how I originally wrote this module. However, I'm aware that
this code base has become a common reference point for beginners, and I think it
is _extremely important_ that slapping some "getters and setters" on a record
does not become a habit for anyone who is getting started with Elm. The whole
point of making the Article type opaque is to create guarantees through
_selectively choosing boundaries_ around it. If you aren't selective about
where those boundaries are, and instead expose a "getter and setter" for every
field in the record, the result is an API with no more guarantees than if you'd
exposed the entire record directly! It is so important to me that beginners not
fall into the terrible "getters and setters" trap that I've exposed this
Metadata record instead of exposing a single function for each of its fields,
as I did originally. This record is not a bad way to do it, by any means,
but if this seems at odds with <https://youtu.be/x1FU3e0sT1I> - now you know why!
See commit c2640ae3abd60262cdaafe6adee3f41d84cd85c3 for how it looked before.
)
-}
type alias Metadata =
{ description : String
, title : String
@@ -89,6 +131,14 @@ type alias Internals =
}
type Preview
= Preview
type Full
= Full Body
-- INFO
@@ -109,8 +159,8 @@ slug (Article internals _) =
body : Article Full -> Body
body _ =
"👉 TODO make this return the article's body"
body (Article _ (Full extraInfo)) =
extraInfo
@@ -131,8 +181,8 @@ mapAuthor transform (Article info extras) =
fromPreview : Body -> Article Preview -> Article Full
fromPreview _ _ =
"👉 TODO convert from an Article Preview to an Article Full"
fromPreview newBody (Article info Preview) =
Article info (Full newBody)
@@ -150,16 +200,7 @@ fullDecoder : Maybe Cred -> Decoder (Article Full)
fullDecoder maybeCred =
Decode.succeed Article
|> custom (internalsDecoder maybeCred)
|> required "body" "👉 TODO use `Body.decoder` (which is a `Decoder Body`) to decode the body into this Article Full"
{- If you're unfamiliar with Decode Pipeline, here's how ☝️ would look without it:
Decode.map2 Article
(internalsDecoder maybeCred)
(Decode.field "body" "use `Body.decoder` (which is a `Decoder Body`) to decode the body into this Article Full")
-}
|> required "body" (Decode.map Full Body.decoder)
internalsDecoder : Maybe Cred -> Decoder Internals

4
advanced/part1/src/Author.elm
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@@ -95,7 +95,7 @@ username : Author -> Username
username author =
case author of
IsViewer cred _ ->
Cred.username cred
cred.username
IsFollowing (FollowedAuthor val _) ->
val
@@ -220,7 +220,7 @@ decodeFromPair maybeCred ( prof, uname ) =
Decode.succeed (IsNotFollowing (UnfollowedAuthor uname prof))
Just cred ->
if uname == Cred.username cred then
if uname == cred.username then
Decode.succeed (IsViewer cred prof)
else

4
advanced/part1/src/Page.elm
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@@ -71,8 +71,8 @@ viewMenu page maybeViewer =
cred =
Viewer.cred viewer
username =
Cred.username cred
{ username } =
cred
avatar =
Profile.avatar (Viewer.profile viewer)

4
advanced/part1/src/Page/Profile.elm
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@@ -88,7 +88,7 @@ view model =
titleForOther (Author.username author)
Loading username ->
if Just username == Maybe.map Cred.username (Session.cred model.session) then
if Just username == Maybe.map .username (Session.cred model.session) then
myProfileTitle
else
@@ -96,7 +96,7 @@ view model =
Failed username ->
-- We can't follow if it hasn't finished loading yet
if Just username == Maybe.map Cred.username (Session.cred model.session) then
if Just username == Maybe.map .username (Session.cred model.session) then
myProfileTitle
else

2
advanced/part1/src/Page/Settings.elm
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@@ -58,7 +58,7 @@ init session =
{ avatar = Avatar.toMaybeString (Profile.avatar profile)
, email = Email.toString (Viewer.email viewer)
, bio = Maybe.withDefault "" (Profile.bio profile)
, username = Username.toString (Cred.username cred)
, username = Username.toString cred.username
, password = Nothing
}

2
advanced/part1/src/Viewer.elm
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@@ -55,7 +55,7 @@ encode : Viewer -> Value
encode (Viewer info) =
Encode.object
[ ( "email", Email.encode info.email )
, ( "username", Username.encode (Cred.username info.cred) )
, ( "username", Username.encode info.cred.username )
, ( "bio", Maybe.withDefault Encode.null (Maybe.map Encode.string (Profile.bio info.profile)) )
, ( "image", Avatar.encode (Profile.avatar info.profile) )
, ( "token", Cred.encodeToken info.cred )

57
advanced/part1/src/Viewer/Cred.elm
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@@ -1,20 +1,4 @@
module Viewer.Cred exposing (Cred, addHeader, addHeaderIfAvailable, decoder, encodeToken, username)
{-| The authentication credentials for the Viewer (that is, the currently logged-in user.)
This includes:
- The cred's Username
- The cred's authentication token
By design, there is no way to access the token directly as a String.
It can be encoded for persistence, and it can be added to a header
to a HttpBuilder for a request, but that's it.
This token should never be rendered to the end user, and with this API, it
can't be!
-}
module Viewer.Cred exposing (Cred, addHeader, addHeaderIfAvailable, decoder, encodeToken)
import HttpBuilder exposing (RequestBuilder, withHeader)
import Json.Decode as Decode exposing (Decoder)
@@ -23,30 +7,21 @@ import Json.Encode as Encode exposing (Value)
import Username exposing (Username)
{-| The authentication token for the currently logged-in user.
The token records the username associated with this token, which you can ask it for.
By design, there is no way to access the token directly as a String. You can encode it for persistence, and you can add it to a header to a HttpBuilder for a request, but that's it.
-}
-- TYPES
type Cred
= Cred Username String
-- INFO
username : Cred -> Username
username (Cred val _) =
val
type alias Cred =
-- 👉 TODO make Cred an opaque type, then fix the resulting compiler errors.
-- Afterwards, it should no longer be possible for any other module to access
-- this `token` vale directly!
--
-- 💡 HINT: Other modules still depend on being able to access the
-- `username` value. Expand this module's API to expose a new way for them
-- to access the `username` without also giving them access to `token`.
{ username : Username
, token : String
}
@@ -65,14 +40,14 @@ decoder =
encodeToken : Cred -> Value
encodeToken (Cred _ str) =
Encode.string str
encodeToken cred =
Encode.string cred.token
addHeader : Cred -> RequestBuilder a -> RequestBuilder a
addHeader (Cred _ str) builder =
addHeader cred builder =
builder
|> withHeader "authorization" ("Token " ++ str)
|> withHeader "authorization" ("Token " ++ cred.token)
addHeaderIfAvailable : Maybe Cred -> RequestBuilder a -> RequestBuilder a