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@flowcadence

JSON-Cadence format

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Last updated at Posted at 2024-10-19

Previous << Contract Upgrades with Incompatible Changes
Next >> Measuring Time In Cadence

JSON-Cadenceは、Cadenceの値を言語に依存しないJSONオブジェクトとして表現するために使用されるデータ交換フォーマットです。
このフォーマットは完全なABIよりも型情報が少なく、代わりに以下の原則を推進しています。

  • 人間にとって読みやすい - JSON-Cadenceは読みやすく理解しやすいので、開発やデバッグのスピードアップにつながります。
  • 互換性 - JSONは、ほとんどの高レベルプログラミング言語に組み込まれたサポート機能を持つ共通フォーマットであるため、さまざまなプラットフォームで簡単に解析できます。
  • 移植性 - JSON-Cadenceは自己記述型であるため、型定義（例えばABI）を伴わずに転送およびデコードが可能です。

Values

Void

{
  "type": "Void"
}

例

{
  "type": "Void"
}

Optional

{
  "type": "Optional",
  "value": null | <value>
}

例

/* Non-nil */

{
  "type": "Optional",
  "value": {
    "type": "UInt8",
    "value": "123"
  }
}

/* Nil */

{
  "type": "Optional",
  "value": null
}

Bool

{
  "type": "Bool",
  "value": true | false
}

例

{
  "type": "Bool",
  "value": true
}

String

{
  "type": "String",
  "value": "..."
}

例

{
  "type": "String",
  "value": "Hello, world!"
}

Address

{
  "type": "Address",
  "value": "0x0" /* as hex-encoded string with 0x prefix */
}

例

{
  "type": "Address",
  "value": "0x1234"
}

Integers

[U]Int, [U]Int8, [U]Int16, [U]Int32, [U]Int64, [U]Int128, [U]Int256, Word8, Word16, Word32, Word64, Word128 or Word256

JSONは64ビットまでの整数リテラルをサポートしていますが、一貫性を保つため、すべての整数型は文字列としてエンコードされます。

デコードには厳密には静的型は必要ありませんが、クライアントに範囲の可能性を通知するために提供されます。

{
  "type": "<type>",
  "value": "<decimal string representation of integer>"
}

例

{
  "type": "UInt8",
  "value": "123"
}

Fixed Point Numbers

[U]Fix64

固定小数点数は整数として実装されていますが、JSON-Cadenceでは可読性を考慮して小数表記を使用しています。

{
  "type": "[U]Fix64",
  "value": "<integer>.<fractional>"
}

例

{
  "type": "Fix64",
  "value": "12.3"
}

Array

{
  "type": "Array",
  "value": [
    <value at index 0>,
    <value at index 1>
    // ...
  ]
}

例

{
  "type": "Array",
  "value": [
    {
      "type": "Int16",
      "value": "123"
    },
    {
      "type": "String",
      "value": "test"
    },
    {
      "type": "Bool",
      "value": true
    }
  ]
}

Dictionary

Dictionaryは、Cadenceによって実装された決定論的順序を維持するために、キーと値のペアのリストとしてエンコードされます。 
{
  "type": "Dictionary",
  "value": [
    {
      "key": "<key>",
      "value": <value>
    },
    ...
  ]
}

例

{
  "type": "Dictionary",
  "value": [
    {
      "key": {
        "type": "UInt8",
        "value": "123"
      },
      "value": {
        "type": "String",
        "value": "test"
      }
    }
  ]
  // ...
}

Composites

(Struct, Resource, Event, Contract, Enum)

Compositeのフィールドは、Compositeの型宣言に現れる順序で、名前と値のペアのリストとしてエンコードされます。(原文: Composite fields are encoded as a list of name-value pairs in the order in which they appear in the composite type declaration.)

{
  "type": "Struct" | "Resource" | "Event" | "Contract" | "Enum",
  "value": {
    "id": "<fully qualified type identifier>",
    "fields": [
      {
        "name": "<field name>",
        "value": <field value>
      },
      // ...
    ]
  }
}

例

{
  "type": "Resource",
  "value": {
    "id": "0x3.GreatContract.GreatNFT",
    "fields": [
      {
        "name": "power",
        "value": { "type": "Int", "value": "1" }
      }
    ]
  }
}

Path

{
  "type": "Path",
  "value": {
    "domain": "storage" | "private" | "public",
    "identifier": "..."
  }
}

例

{
  "type": "Path",
  "value": {
    "domain": "storage",
    "identifier": "flowTokenVault"
  }
}

Type Value

{
  "type": "Type",
  "value": {
    "staticType": <type>
  }
}

例

{
  "type": "Type",
  "value": {
    "staticType": {
      "kind": "Int"
    }
  }
}

InclusiveRange

{
  "type": "InclusiveRange",
  "value": {
    "start": <start_value>,
    "end": <end_value>,
    "step": <step_value>
  }
}

例

{
  "type": "InclusiveRange",
  "value": {
    "start": {
      "type": "Int256",
      "value": "10"
    },
    "end": {
      "type": "Int256",
      "value": "20"
    },
    "step": {
      "type": "Int256",
      "value": "5"
    }
  }
}

Capability

{
  "type": "Capability",
  "value": {
    "id": <Number>,
    "address": "0x0",  /* as hex-encoded string with 0x prefix */
    "borrowType": <type>,
  }
}

例

{
  "type": "Capability",
  "value": {
    "id": "1",
    "address": "0x1",
    "borrowType": {
      "kind": "Int"
    }
  }
}

Functions

{
  "type": "Function",
  "value": {
    "functionType": <type>
  }
}

Functionの値はエクスポートのみ可能で、インポートはできません。

例

{
  "type": "Function",
  "value": {
    "functionType": {
      "kind": "Function",
      "typeID": "fun():Void",
      "parameters": [],
      "return": {
        "kind": "Void"
      }
    }
  }
}

Types

Simple Types

これらは、Int、String、StoragePathのような基本的な型です。

{
  "kind": <kind>
}

ここでkindは次のいずれかです。

  • Account
  • AccountCapabilityController
  • AccountKey
  • Address
  • AnyResource
  • AnyResourceAttachment
  • AnyStruct
  • AnyStructAttachment
  • Block
  • Bool
  • Capability
  • CapabilityPath
  • Character
  • DeployedContract
  • DeploymentResult
  • Fix64
  • FixedPoint
  • FixedSizeUnsignedInteger
  • HashAlgorithm
  • HashableStruct
  • Int
  • Int128
  • Int16
  • Int256
  • Int32
  • Int64
  • Int8
  • Integer
  • Never
  • Number
  • Path
  • PrivatePath
  • PublicKey
  • PublicPath
  • SignatureAlgorithm
  • SignedFixedPoint
  • SignedInteger
  • SignedNumber
  • StorageCapabilityController
  • StoragePath
  • String
  • Type
  • UFix64
  • UInt
  • UInt128
  • UInt16
  • UInt256
  • UInt32
  • UInt64
  • UInt8
  • Void
  • Word128
  • Word16
  • Word256
  • Word32
  • Word64
  • Word8

例

{
  "kind": "UInt8"
}

Optional Types

{
  "kind": "Optional",
  "type": <type>
}

例

{
  "kind": "Optional",
  "type": {
    "kind": "String"
  }
}

Variable Sized Array Types

{
  "kind": "VariableSizedArray",
  "type": <type>
}

例

{
  "kind": "VariableSizedArray",
  "type": {
    "kind": "String"
  }
}

Constant Sized Array Types

{
  "kind": "ConstantSizedArray",
  "type": <type>,
  "size": <length of array>,
}

例

{
  "kind": "ConstantSizedArray",
  "type": {
    "kind": "String"
  },
  "size": 3
}

Dictionary Types

{
  "kind": "Dictionary",
  "key": <type>,
  "value": <type>
}

例

{
  "kind": "Dictionary",
  "key": {
    "kind": "String"
  },
  "value": {
    "kind": "UInt16"
  }
}

Composite Types

{
  "kind": "Struct" | "Resource" | "Event" | "Contract" | "StructInterface" | "ResourceInterface" | "ContractInterface",
  "type": "", /* this field exists only to keep parity with the enum structure below; the value must be the empty string */
  "typeID": "<fully qualified type ID>",
  "initializers": [
    <initializer at index 0>,
    <initializer at index 1>
    /* ... */
  ],
  "fields": [
    <field at index 0>,
    <field at index 1>
    /* ... */
  ],
}

例

{
  "kind": "Resource",
  "type": "",
  "typeID": "0x3.GreatContract.GreatNFT",
  "initializers": [
    [
      {
        "label": "foo",
        "id": "bar",
        "type": {
          "kind": "String"
        }
      }
    ]
  ],
  "fields": [
    {
      "id": "foo",
      "type": {
        "kind": "String"
      }
    }
  ]
}

Field Types

{
  "id": "<name of field>",
  "type": <type>
}

例

{
  "id": "foo",
  "type": {
    "kind": "String"
  }
}

Parameter Types

{
  "label": "<label>",
  "id": "<identifier>",
  "type": <type>
}

例

{
  "label": "foo",
  "id": "bar",
  "type": {
    "kind": "String"
  }
}

Initializer Types

初期化子型には、初期化子(init関数)へのパラメータのリストがエンコードされています。

[
  <parameter at index 0>,
  <parameter at index 1>,
  /* ... */
]

例

[
  {
    "label": "foo",
    "id": "bar",
    "type": {
      "kind": "String"
    }
  }
]

Function Types

{
  "kind": "Function",
  "typeID": "<function name>",
  "parameters": [
    <parameter at index 0>,
    <parameter at index 1>,
    /* ... */
  ],
  "purity: "view" | undefined,
  "return": <type>
}

例

{
  "kind": "Function",
  "typeID": "foo",
  "parameters": [
    {
      "label": "foo",
      "id": "bar",
      "type": {
        "kind": "String"
      }
    }
  ],
  "purity": "view",
  "return": {
    "kind": "String"
  }
}

Reference Types

{
  "kind": "Reference",
  "authorization": {
    "kind": "Unauthorized" | "EntitlementMapAuthorization" | "EntitlementConjunctionSet" | "EntitlementDisjunctionSet",
    "entitlements": [
    <entitlement at index 0>,
    <entitlement at index 1>
    /* ... */
    ]
    },
  "type": <type>
}

例

{
  "kind": "Reference",
  "authorization": {
    {
      "kind": "EntitlementMapAuthorization",
      "entitlements": [
        {
          "kind": "EntitlementMap",
          "typeID": "foo"
        }
      ]
    }
  },
  "type": {
    "kind": "String"
  }
}

Intersection Types

{
  "kind": "Intersection",
  "typeID": "<fully qualified type ID>",
  "types": [
    <type at index 0>,
    <type at index 1>,
    /* ... */
  ]
}

例

{
  "kind": "Intersection",
  "typeID": "{0x1.FungibleToken.Receiver}",
  "types": [
    {
      "kind": "ResourceInterface",
      "typeID": "0x1.FungibleToken.Receiver",
      "fields": [
        {
          "id": "uuid",
          "type": {
            "kind": "UInt64"
          }
        }
      ],
      "initializers": [],
      "type": ""
    }
  ]
}

Capability Types

{
  "kind": "Capability",
  "type": <type>
}

例

{
  "kind": "Capability",
  "type": {
    "kind": "Reference",
    "authorization": {
      "kind": "Unauthorized",
      "entitlements": null
    },
    "type": {
      "kind": "String"
    }
  }
}

Enum Types

{
  "kind": "Enum",
  "type": <type>,
  "typeID": "<fully qualified type ID>",
  "initializers":[],
  "fields": [
    {
      "id": "rawValue",
      "type": <type>
    }
  ]
}

例

{
  "kind": "Enum",
  "type": {
    "kind": "String"
  },
  "typeID": "0x3.GreatContract.GreatEnum",
  "initializers": [],
  "fields": [
    {
      "id": "rawValue",
      "type": {
        "kind": "String"
      }
    }
  ]
}

Repeated Types

複合型が同じJSON型エンコーディング内で複数回現れる場合、それは再帰的であるか、または（複合フィールド内で）繰り返されるためであり、その複合型は代わりにその型IDで表されます。

例

{
  "type": "Type",
  "value": {
    "staticType": {
      "kind": "Resource",
      "typeID": "0x3.GreatContract.NFT",
      "fields": [
        {
          "id": "foo",
          "type": {
            "kind": "Optional",
            "type": "0x3.GreatContract.NFT"
                    /* recursive NFT resource type is instead encoded as an ID */
          }
        }
      ],
      "initializers": [],
      "type": ""
    }
  }
}

Inclusive Range Type

{
  "kind": "InclusiveRange",
  "element":  <integer_type>
}

例

{
  "kind": "InclusiveRange",
  "element": {
    "kind": "Int"
  }
}

翻訳元

Previous << Contract Upgrades with Incompatible Changes

Flow blockchain / Cadence version1.0ドキュメント (JSON-Cadence format)

Next >> Measuring Time In Cadence

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