Safe Haskell	Safe-Inferred
Language	Haskell2010

Hakyll.Core.Identifier

Description

An identifier is a type used to uniquely name an item. An identifier is similar to a file path, but can contain additional details (e.g. item's version). Examples of identifiers are:

```
posts/foo.markdown
```
```
index
```
```
error/404
```

See Identifier for details.

Synopsis

data Identifier
fromFilePath :: FilePath -> Identifier
toFilePath :: Identifier -> FilePath
identifierVersion :: Identifier -> Maybe String
setVersion :: Maybe String -> Identifier -> Identifier

Documentation

data Identifier Source #

A key data type to identify a compiled Item in the Store. Conceptually, it's a combination of a file path and a version name. The version is used only when a file is compiled within a rule using the version wrapper function (the same source file can be compiled into several items in the store, so the version exists to distinguish them). Use functions like fromFilePath, setVersion, getMatches to build an Identifier.

Usage Examples

Expand

Normally, compiled items are saved to the store by Rules with an automatic, implicit identifier and loaded from the store by the user in another rule with a manual, explicit identifier.

Identifiers when using match. Using match builds an implicit identifier that corresponds to the expanded, relative path of the source file on disk (relative to the project directory configured with providerDirectory):

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                                          -- saved with implicit identifier 'posts/hakyll.md'
    compile pandocCompiler

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md") -- load with explicit identifier
        ...

Normally, the identifier is only explicitly created to pass to one of the load functions.

Identifiers when using create. Using create (thereby inventing a file path with no underlying file on disk) builds an implicit identifier that corresponds to the invented file path:

create ["index.html"] $ do                                -- saved with implicit identifier 'index.html'
    compile $ makeItem ("Hello world" :: String)

match "about/*" $ do
    compile $ do
        compiledIndex <- load (fromFilePath "index.html") -- load with an explicit identifier
        ...

Identifiers when using versions. With version the same file can be compiled into several items in the store. A version name is needed to distinguish them:

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                              -- saved with implicit identifier ('posts/hakyll.md', no-version)
    compile pandocCompiler

match "posts/*" $ version "raw" $ do              -- saved with implicit identifier ('posts/hakyll.md', version raw)
    compile getResourceBody

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md")                      -- load no-version version
        rawPost <- load . setVersion (Just "raw") $ fromFilePath "posts/hakyll.md" -- load version raw
    ...

Use setVersion to set (or replace) the version of an identifier like fromFilePath "posts/hakyll.md".

Instances

Instances details

IsString Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods fromString :: String -> Identifier #
Show Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods showsPrec :: Int -> Identifier -> ShowS # show :: Identifier -> String # showList :: [Identifier] -> ShowS #
Binary Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods put :: Identifier -> Put # get :: Get Identifier # putList :: [Identifier] -> Put #
NFData Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods rnf :: Identifier -> () #
Eq Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods (==) :: Identifier -> Identifier -> Bool # (/=) :: Identifier -> Identifier -> Bool #
Ord Identifier Source #
Instance details Defined in Hakyll.Core.Identifier Methods compare :: Identifier -> Identifier -> Ordering # (<) :: Identifier -> Identifier -> Bool # (<=) :: Identifier -> Identifier -> Bool # (>) :: Identifier -> Identifier -> Bool # (>=) :: Identifier -> Identifier -> Bool # max :: Identifier -> Identifier -> Identifier # min :: Identifier -> Identifier -> Identifier #

fromFilePath :: FilePath -> Identifier Source #

Parse an identifier from a file path string. For example,

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                                          -- saved with implicit identifier 'posts/hakyll.md'
    compile pandocCompiler

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md") -- load with explicit identifier
        ...

toFilePath :: Identifier -> FilePath Source #

Convert an identifier back to a relative FilePath.

identifierVersion :: Identifier -> Maybe String Source #

setVersion :: Maybe String -> Identifier -> Identifier Source #

Set or override the version of an identifier in order to specify which version of an Item to load from the Store. For example,

match "posts/*" $ version "raw" $ do              -- saved with implicit identifier ('posts/hakyll.md', version raw)
    compile getResourceBody

match "about/*" $ do
    compile $ do
        rawPost <- load . setVersion (Just "raw") $ fromFilePath "posts/hakyll.md" -- load version raw
        ...