substrate_metadata

Description:

substrate metadata

substrate_metadata #
substrate_metadata is a flutter and dart library for encoding and decoding chain metadata, constants, extrinsics and events of blocks.
Lets Get Started #
Decode Metadata #
// decoded metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

//
// get raw Map<String, dynamic>
final rawMetadata = decodedMetadata.metadataJson;

//
// get Metadata Object
final metadataObject = decodedMetadata.metadataObject;
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Create ChainInfo from Metadata #
// decoded metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);
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Decode Extrinsic #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

final String extrinsicHex = '0x990403......a2f9e184';

// Create extrinsics input
final input = Input.fromHex(extrinsicHex);

// decode extrinsic
final dynamic decoded = ExtrinsicsCodec(chainInfo: chainInfo).decode(input);
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Encode Extrinsic #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

// Create Output
final output = HexOutput();

final Map<String, dynamic> extrinsicsMap = {'version': 4, 'signature': ....... };

// encode extrinsic
ExtrinsicsCodec(chainInfo: chainInfo).encodeTo(extrinsicsMap, output);

// encoded extrinsics Hex
final extrinsicsHex = output.toString();
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Decode Events #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

final String encodedEventsHex = '0x38000dd14c4572......................5ec6e6fcd6184d952d000000';

final input = Input.fromHex(encodedEventsHex);

// list of decoded events
final List<dynamic> decodedEvents = chainInfo.scaleCodec.decode('EventCodec', input);
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Encode Events #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

final Map<String, dynamic> events = [{ 'phase': {'ApplyExtrinsic': 0}, 'event': {....} }];

final output = HexOutput();

// encode the events
chainInfo.scaleCodec.encodeTo('EventCodec', events, output);

// events hex
final eventsHex = output.toString();
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Decode Constants #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

//
// Look on constants of chain description
for (final palletMapEntry in chainInfo.constants.entries) {

//
// Loop throught all the constants in this given pallet
for (final constantMapEntry in palletMapEntry.value.entries) {
final Constant originalConstant = constantMapEntry.value;

//
// Encoded Constant bytes
final encodedBytes = originalConstant.bytes;

//
// Decoded Constant value
final decoded = originalConstant.value;
}
}
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Encode Constants #
// decode metadata
final DecodedMetadata decodedMetadata = MetadataDecoder.instance.decode('0x6d657.....790b807d0b');

// create ChainInfo from metadata
final ChainInfo chainInfo = ChainInfo.fromMetadata(decodedMetadata);

final output = ByteOutput();

final decodedConstantValue = /** Some constant value from originalConstant **/;

originalConstant.type.encodeTo(decodedConstantValue, output);

final encodedConstant = output.toBytes();
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Add SpecVersion #
final specJson = {'specName': 'polkadot', 'specVersion':......};

final specVersion = SpecVersion.fromJson(specJson);

// specVersion gets added to support decoding the blocks.
chainObject.addSpecVersion(specVersion);
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Create ChainInfo from SpecVersion #
// when using preV14 metadata
final chainDefinitions = LegacyTypesBundle.fromJson(chainJson);
final Chain chain = Chain(chainDefinitions);

// or

// when using V14 metadata, you don't need to provide chainDefinitions
final Chain chain = Chain();

final specJson = {'specName': 'polkadot', 'specVersion':......};

final SpecVersion specVersion = SpecVersion.fromJson(specJson);

final ChainInfo chainInfo = chain.getChainInfoFromSpecVersion(specVersion);
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Decode Extrinsic (With Chain) #
// when using preV14 metadata
final chainDefinitions = LegacyTypesBundle.fromJson(chainJson);
final Chain chain = Chain(chainDefinitions);

// or

// when using V14 metadata, you don't need to provide chainDefinitions
final Chain chain = Chain();

// Preferred to provide all the available Spec-Version information.
chain.initSpecVersionFromFile('../chain/versions.json');

final RawBlock rawBlock = RawBlock.fromJson( { blockJson } );

// DecodedBlockExtrinsics
final DecodedBlockExtrinsics decodedExtrinsic = chain.decodeExtrinsics(rawBlock);
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Encode Extrinsic (With Chain) #
// when using preV14 metadata
final chainDefinitions = LegacyTypesBundle.fromJson(chainJson);
final Chain chain = Chain(chainDefinitions);

// or

// when using V14 metadata, you don't need to provide chainDefinitions
final Chain chain = Chain();

// Preferred to provide all the available Spec-Version information.
chain.initSpecVersionFromFile('../chain/versions.json');

final RawBlock rawBlock = RawBlock.fromJson( { blockJson } );

// DecodedBlockExtrinsics
final DecodedBlockExtrinsics decodedExtrinsic = chain.decodeExtrinsics(rawBlock);

// encodedRawBlock.hashCode == rawBlock
final RawBlock encodedRawBlock = chain.encodeExtrinsic(decodedExtrinsic);
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Decode Events (With Chain) #
// when using preV14 metadata
final chainDefinitions = LegacyTypesBundle.fromJson(chainJson);
final Chain chain = Chain(chainDefinitions);

// or

// when using V14 metadata, you don't need to provide chainDefinitions
final Chain chain = Chain();

// Preferred to provide all the available Spec-Version information.
chain.initSpecVersionFromFile('../chain/versions.json');

final RawBlockEvents rawBlockEvents = RawBlockEvents.fromJson( { blockJson } );

// DecodedBlockEvents
final DecodedBlockEvents decodedEvents = chain.decodeEvents(rawBlockEvents);
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Encode Events (With Chain) #
// when using preV14 metadata
final chainDefinitions = LegacyTypesBundle.fromJson(chainJson);
final Chain chain = Chain(chainDefinitions);

// or

// when using V14 metadata, you don't need to provide chainDefinitions
final Chain chain = Chain();

// Preferred to provide all the available Spec-Version information.
chain.initSpecVersionFromFile('../chain/versions.json');

final rawBlockEvents = RawBlockEvents.fromJson( { blockJson } );

// DecodedBlockEvents
final DecodedBlockEvents decodedEvents = chain.decodeEvents(rawBlockEvents);

// encodedBlockEvents.hashCode == rawBlockEvents.hashCode
final RawBlockEvents encodedBlockEvents = chain.encodeEvents(decodedEvents);
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Resources #

substrate.dev
Parity-scale-codec
Polkadot.js
Squid