14 getin (#15)

* implments GetIn * pump version to 0.4.0 * update doc close #14
robertluo · Aug 8, 2019 · ae6dd09 · ae6dd09
1 parent d57f4f4
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diff --git a/README.md b/README.md
@@ -5,6 +5,8 @@ My attempt of implementing [Edn format](https://github.com/edn-format/edn) for .
 
 ## Usage
 
+### Parse
+
 ```F#
 open Robertluo
 
@@ -28,9 +30,21 @@ var b = Edn.VecOf(new Edn[] { Edn.Kw("foo", "bar"), Edn.NewEBool(false), Edn.New
 var b = Edn.Parse("[:foo/bar, false, \"Hello\"]");
 ```
 
+### GetIn
+
+`GetIn` can quickly pull value from a EDN value.
+
+```c#
+/// Get in can 
+var c = Edn.Parse("[{:a 3 :b \"ok\"} {:a 15, :b nil}]");
+WriteLine($"Get in: {c.GetIn(new Edn[] {Edn.NewEInteger(1L), Edn.Kw(null, "a")})}");
+```
+
 ## Releases
 
  - 0.2.0 with all standard features implemented
+ - 0.3.0 with some constructor for c# programmer convinience
+ - 0.4.0 introduce `GetIn`
 
 ## Design
 

diff --git a/src/Edn.Net/Edn.Net.fsproj b/src/Edn.Net/Edn.Net.fsproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <PackageId>Robertluo.Edn</PackageId>
-    <version>0.3.0</version>
+    <version>0.4.0</version>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Library.fs" />

diff --git a/src/Edn.Net/Library.fs b/src/Edn.Net/Library.fs
@@ -197,8 +197,30 @@ module Edn =
                     esymbol; estring; etagged ] .>> ws
 
     //-------------- Interface ---------------
+    /// Parse a string into a Edn value
     let parse = run evalue
 
+    /// Get value from edn on path
+    let rec getIn (path : Edn list) (edn : Edn) : Edn =
+        match edn with
+        | EVector v ->
+            match path with
+            | [] -> edn
+            | x :: xs ->
+                match x with
+                | EInteger i -> v.GetValue i :?> Edn |> getIn xs
+                | _ -> failwith "vector can only support integer path"
+        | EMap m ->
+            match path with
+            | [] -> edn
+            | x :: xs -> Map.find x m |> getIn xs
+        | v ->
+            match path with
+            | [] -> edn
+            | _ :: _ ->
+                invalidOp
+                    (sprintf "Edn v (%s) does not support GetIn" (v.ToString()))
+
 //-------------- Attach functions to type --------------
 exception ParseException of string * ParserError
 
@@ -212,6 +234,9 @@ type Edn with
           Name = sym }
         |> EKeyword
 
+    /// Get value specified by path
+    member this.GetIn(path) = Edn.getIn (List.ofArray path) this
+
     /// Shortcut for creating EVector from an array
     static member VecOf(elems) = EVector elems
 

diff --git a/src/Trial/Program.cs b/src/Trial/Program.cs
@@ -10,14 +10,17 @@ static void Main(string[] args)
         {
             var v = Edn.Parse("{:foo/bar 35 :name \"Hello\"}");
             var u = v.IsEMap ? ((Edn.EMap) v).Item : null;
-            
+
             var a = Edn.MapOf(new Tuple<Edn, Edn>[] {new Tuple<Edn, Edn>(Edn.Kw(null, "foo"), Edn.NewEInteger(3L))});
             WriteLine($"a should be: {a}");
             WriteLine($"equals to: {Edn.Parse("{:foo 3}")}");
-            
-            var b = Edn.VecOf(new Edn[] { Edn.Kw("foo", "bar"), Edn.NewEBool(false), Edn.NewEString("hello")});
+
+            var b = Edn.VecOf(new Edn[] {Edn.Kw("foo", "bar"), Edn.NewEBool(false), Edn.NewEString("hello")});
             WriteLine($"b should be: {b}");
             WriteLine($"equals to: {Edn.Parse("[:foo/bar, false, \"hello\"]")}");
+
+            var c = Edn.Parse("[{:a 3 :b \"ok\"} {:a 15, :b nil}]");
+            WriteLine($"Get in: {c.GetIn(new Edn[] {Edn.NewEInteger(1L), Edn.Kw(null, "a")})}");
         }
     }
-}
+}
diff --git a/test/Edn.Net.Test/Tests.fs b/test/Edn.Net.Test/Tests.fs
@@ -91,7 +91,7 @@ let tests =
               | v -> failtestf "not understandable: %A" v ]
 
 [<Tests>]
-let test2 =
+let testToString =
     testList "ToString"
         [ testCase "keyword" <| fun _ ->
               let input =
@@ -125,4 +125,18 @@ let testMisc =
           <| fun _ ->
               let input = "[3:foo"
               Expect.throws (fun () -> (Edn.Parse input) |> ignore)
+                  "should throw"
+
+          testCase "when get in a valid value"
+          <| fun _ ->
+              let input = Edn.Parse "[{:a 3 :b true} {:a 5 :b false}]"
+              Expect.equal (Edn.getIn [ EInteger 1L
+                                        Edn.Kw(null, "a") ] input) (EInteger 5L)
+                  "should find value"
+
+          testCase "when specify an invalid path"
+          <| fun _ ->
+              let input = Edn.Parse "[[1 \"ok\"]]"
+              Expect.throws
+                  (fun () -> Edn.getIn [ EInteger 2L ] input |> ignore)
                   "should throw" ]