441d09c4a7
- Copy documentation from elm-lang.org (dev branch) to .elm files in libraries folder - Added TODO's for stuff that was not found in 0.8 version - Added Review TODO in json.elm
91 lines
3.3 KiB
Elm
91 lines
3.3 KiB
Elm
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-- TOOD: Evan please review texts
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module Json where
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import Dict as Dict
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import JavaScript as JS
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import Native.Json as Native
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-- This datatype can represent all valid values that can be held in a JSON object.
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-- In Elm, a proper JSON object is represented as a (Dict String Value) which is a mapping from strings to Json Values.
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data Value
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= String String
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| Number Float
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| Boolean Bool
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| Null
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| Array [Value]
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| Object (Dict String Value)
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-- String Converters
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-- Convert a proper JSON object into a string.
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toString : Value -> String
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toString v = JS.toString (Native.toPrettyJSString "" v)
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-- Convert a proper JSON object into a prettified string.
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-- The first argument is a separator token (e.g. \" \", \"\\n\", etc.) that will be used for indentation in the prettified string version of the JSON object.
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toPrettyString : String -> Value -> String
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toPrettyString sep v = JS.toString (Native.toPrettyJSString sep v)
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-- Convert a proper JSON object into a JavaScript string.
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-- Note that the type JSString seen here is not the same as the type constructor JsonString used elsewhere in this module.
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toJSString : Value -> JSString
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toJSString v = Native.toPrettyJSString "" v
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-- Parse a string representation of a proper JSON object into its Elm's representation.
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fromString : String -> Maybe Value
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fromString s = Native.fromJSString (JS.fromString s)
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-- Parse a JavaScript string representation of a proper JSON object into its Elm's representation.
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fromJSString : JSString -> Maybe Value
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-- Extract Elm values from Json values
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string : Value -> String
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string v = case v of { String s -> s ; _ -> "" }
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number : Value -> Float
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number v = case v of { Number n -> n ; _ -> 0 }
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boolean : Value -> Bool
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boolean v = case v of { Boolean b -> b ; _ -> False }
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array : Value -> [Value]
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array v = case v of { Array a -> a ; _ -> [] }
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object : Value -> Dict String Value
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object v = case v of { Object o -> o ; _ -> Dict.empty }
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-- Extract Elm values from dictionaries of Json values
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-- Find a value in a Json Object using the passed get function. If the key is not found, this returns the given default/base value.
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find get base =
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let f key dict =
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case Dict.lookup key dict of
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Nothing -> base
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Just v -> get v
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in f
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-- Find a string value in an Elm Json object. If the key is not found or the value found is not a string, this returns the empty string.
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findString : String -> Dict String Value -> String
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findString = find string ""
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-- Find a number value in an Elm Json object. If the key is not found or the value found is not a number, this returns 0
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findNumber : String -> Dict String Value -> Float
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findNumber = find number 0
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-- Find a boolean value in an Elm Json object. If the key is not found or the value found is not a boolean, this returns the False.
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findBoolean : String -> Dict String Value -> Bool
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findBoolean = find boolean False
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-- Find an array value in an Elm Json object. If the key is not found or the value found is not an array, this returns an empty list.
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findArray : String -> Dict String Value -> [Value]
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findArray = find array []
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-- Find an object value in an Elm Json object. If the key is not found or the value found is not an object, this returns an empty object.
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findObject : String -> Dict String Value -> Dict String Value
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findObject = find object Dict.empty
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