documentation for json codec backend

finos · AttilaMihaly · Feb 9, 2023 · Feb 1, 2023 · Feb 7, 2023 · Feb 8, 2023
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+## Json Codec Backend
+The purpose of this documentation is to give a explanation of how the Json Codec Backend works and how to use it.
+The Json Codec backend is a tool that generates encoders and decoders from a Morphir IR using the Circe JSON library.
+
+### How to use the JSON Codec Backend
+
+The first step to using the JSON Codec backend is to add the Circe JSON library to your project. This can be done in two ways:
+1. Add the Circe JSON dependency through your build tool eg. Sbt, Mill etc.
+2. Add ```morphir-jvm``` as a dependency to your project.
+
+#### Generating Codecs from the IR
+The backend is built to generate codecs for only types so when generating an IR the ```-t``` which specifies ```--types-only``` flag should be used. Also, we want to add the ```-f``` flag to use the old CLI make function.
+
+To generate Codecs from the  IR:
+1. Run ```morphir-elm make -f -t``` to generate the IR.
+2.  Run ```morphir-elm gen -s``` to generate the codecs
+3.  In the situation where you do not have ```morphir-jvm``` as a dependency in your project, you have to add the ```-c``` flag to copy dependencies from the ```morphir-jvm``` project. Complete command for this is ```morphir-elm gen -s -c```
+
+### How to use Generated Codecs
+Using an example , lets describe a model structure and look at how the generated codec for this particular model will be structured
+
+The model:
+
+	- reference-model
+      - src
+        - Morphir
+          - Reference
+	        - Model
+              - BooksAndRecords.elm  
+	- morphir.json
+	- morphir-ir.json
+
+
+Running the command  ```morphir-elm gen -s -c -o codecs/src``` to generate codecs means your codecs would be outputted into the ``` codecs/src```  folder in the structure:
+
+	- reference-model
+	  - codecs
+        - src
+          - morphir
+		    - booksandrecords
+                  - Codec.scala   <----- This is your genereated codec 
+	- morphir.json
+	- morphir-ir.json
+
+The generated codecs ```Codec.scala```  has both encoders and decoders. Encoders at the top and decoders following. This is a truncated example of how it looks:
+```
+package morphir.reference.model.booksandrecords  
+
+
+object Codec{
+	encoders ...
+
+	decoders ...
+}
+```
+
+In the example above ```myproject``` is the project in which the codecs would be used.
+The codecs can now be imported into ```myproject```  and used.
+
+
+
+#### Unsupported Features
+Codecs are not generated for Function types in the morphir ir.
+
+
+
+