[hakyll] Adding a field to items loaded with loadAll

[Beerend Lauwers]

Hi all, I'd like to do the following: load a bunch of content with loadAll
and iterate over it in a for loop in a template. This part is trivial to do:

howDoIPosts <- loadAll "content/how-do-i/*/*"
let ctx = listField "how-do-i-posts" defaultContext (return howDoIPosts)

But now, I would like to add a new key to each element loaded by loadAll, a
calculated one: the value of the item's URL without its file extension,
which should be available in $url-plain$.

I've looked around in the source code, but it's not obvious to me how I
should go about this.

Does anyone have experience with this?

Kind Regards,
Beerend Lauwers

[Jasper Van der Jeugt]

Hello Beerend,

Each element in the list is rendered with the `Context` you pass in. In
your case, this is `defaultContext`. You can add this new key by simply
extending this context.

First we define a function which does what you want:

import System.FilePath (dropExtension)

urlPlainField :: Context a
urlPlainField = field "url-plain" $ \item -> do
mbFilePath <- getRoute (itemIdentifier item)
case mbFilePath of
Nothing -> return "???"
Just filePath -> return $ toUrl $ dropExtension filePath

And then we add it to some `Context` that we define for the use in the
list:

postCtx :: Context String
postCtx =
urlPlainField `mappend`
defaultContext

Now, the following should enable you to use the new `$url-plain$`:

let ctx = listField "how-do-i-posts" postCtx (return howDoIPosts)

Hope this helps,
Peace,
Jasper

Post by Beerend Lauwers
Hi all, I'd like to do the following: load a bunch of content with loadAll
howDoIPosts <- loadAll "content/how-do-i/*/*"
let ctx = listField "how-do-i-posts" defaultContext (return howDoIPosts)
But now, I would like to add a new key to each element loaded by loadAll, a
calculated one: the value of the item's URL without its file extension,
which should be available in $url-plain$.
I've looked around in the source code, but it's not obvious to me how I
should go about this.
Does anyone have experience with this?
Kind Regards,
Beerend Lauwers
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[Beerend Lauwers]

Awesome! Thanks! I made this into a blog post, because I wanted to
understand *why* this was the
solution: http://beerendlauwers.be/posts/2016-04-29-hakyll-adding-to-loadall.html

(If I misinterpreted anything in there, feel free to correct me ;) )

Thanks again!

Beerend

Post by Jasper Van der Jeugt
Hello Beerend,
Each element in the list is rendered with the `Context` you pass in. In
your case, this is `defaultContext`. You can add this new key by simply
extending this context.
import System.FilePath (dropExtension)
urlPlainField :: Context a
urlPlainField = field "url-plain" $ \item -> do
mbFilePath <- getRoute (itemIdentifier item)
case mbFilePath of
Nothing -> return "???"
Just filePath -> return $ toUrl $ dropExtension filePath
And then we add it to some `Context` that we define for the use in the
postCtx :: Context String
postCtx =
urlPlainField `mappend`
defaultContext
let ctx = listField "how-do-i-posts" postCtx (return howDoIPosts)
Hope this helps,
Peace,
Jasper

Post by Beerend Lauwers
Hi all, I'd like to do the following: load a bunch of content with

loadAll

Post by Beerend Lauwers
and iterate over it in a for loop in a template. This part is trivial to
howDoIPosts <- loadAll "content/how-do-i/*/*"
let ctx = listField "how-do-i-posts" defaultContext (return howDoIPosts)
But now, I would like to add a new key to each element loaded by

loadAll, a

Post by Beerend Lauwers
calculated one: the value of the item's URL without its file extension,
which should be available in $url-plain$.
I've looked around in the source code, but it's not obvious to me how I
should go about this.
Does anyone have experience with this?
Kind Regards,
Beerend Lauwers
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