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  • int: in SCALE integers can be encoded as fixed-width integer and compact integer. Compact integer itself has 4 modes. So generally we have 5 ways to serde integer (1 fixed-width + 4 modes of compact integers) 

    Code Block
    languagebash
    {
	"type": "int",
	"mode": "CompactTwoByte" //possible values FixedWidth, CompactSingleByte, CompactTwoByte, CompactFourByte, CompactBigInteger,
}


  • bool: no tricks here 


    Code Block
    languagebash
    {
	"type": "bool"
}


2. Built-in containers 

  • [Option / Result / Vec / typle : basically we are interested in only inner values of the container


    Code Block
    [
{
    "type": "Option",
    "item_type": {
        "type" : "bool"
    }

},
{
    "type": "Result",
    "item_type": {
        "type": "int",
        "mode": "CompactFourByte"
    }
},
{
    "type": "Vec",
    "item_type": {
        "type": "bool"
    }
},
{
    "type": "tuple",
    "items": [
        {
            "type": "int",
            "mode": "CompactFourByte"
        },
        {
            "type": "Option",
            "item_type": {
                "type" : "bool"
            }
        
        }
    ]
}
]


...

  • Structures: in structures declare definitions inline for built-in types and declare a reference for custom types 


    Code Block
    languagebash
    {
    "type": "struct",
    "name": "Foo",
    "codec": "SCALE", //possible values SCALE or JSON
    "properties": [
        {
            "name": "enabled", //optional name
            "definition": {
                "type": "bool"
            }
        },
        {
            "name": "id", //optional name
            "definition": {
                "type": "struct", //reference to other struct
                "struct_name": "Id"
            }
        },
        {
            "name": "counter", //optional name
            "definition": {
                "type": "int",
                "mode": "FixedWidth"
            }
        }
    ]
}


  • Enums: similar to Structures but also every variant of enum has a discriminator that used in Scale. By default based on 0, but can be overriden by attributes


    Code Block
    {
    "type": "enum",
    "name": "Bar",
    "codec": "SCALE", //possible values SCALE or JSON
    "variants": [
        {
            "name": "FirstVariant",
            "discriminator": 1,
            "properties": {
                ...
            }
        },
        {
            "name": "SecondVariant",
            "discriminator": 2,
            "properties": {
                ...
            }
        }
    ]
}



Additional Information

  1. Scale codec description in Substrate docs [https://substrate.dev/docs/en/knowledgebase/advanced/codec]
  2. Scale codec Github page [https://github.com/paritytech/parity-scale-codec]