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Examples

Code Examples

Encode a Call

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runtime_config = RuntimeConfigurationObject()

# This types are all hardcoded types needed to decode metadata types
runtime_config.update_type_registry(load_type_registry_preset(name="core"))

# Decode retrieved metadata from the RPC
metadata = runtime_config.create_scale_object(
    'MetadataVersioned', data=ScaleBytes(response.get('result'))
)
metadata.decode()

# Add the embedded type registry to the runtime config
runtime_config.add_portable_registry(metadata)

call = runtime_config.create_scale_object(
    "Call", metadata=metadata
)
call.encode({
    "call_module": "Balances",
    "call_function": "transfer",
    "call_args": {"dest": "5GNJqTPyNqANBkUVMN1LPPrxXnFouWXoe2wNSmmEoLctxiZY", "value": 3},
})

Decode the result of a state_getStorageAt RPC call

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event_data = "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"

system_pallet = metadata.get_metadata_pallet("System")
event_storage_function = system_pallet.get_storage_function("Events")

event = runtime_config.create_scale_object(
    event_storage_function.get_value_type_string(), metadata=metadata
)
print(event.decode(ScaleBytes(event_data)))

Generate type decomposition information

The function generate_type_decomposition can be used when more information is needed how to encode a certain SCALE type:

Example 1 

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scale_obj = runtime_config.create_scale_object("RawBabePreDigest")

type_info = scale_obj.generate_type_decomposition()

print(type_info)
# {
#   'Phantom': None, 
#   'Primary': {'authority_index': 'u32', 'slot_number': 'u64', 'vrf_output': '[u8; 32]', 'vrf_proof': '[u8; 64]'}, 
#   'SecondaryPlain': {'authority_index': 'u32', 'slot_number': 'u64'}, 
#   'SecondaryVRF': {'authority_index': 'u32', 'slot_number': 'u64', 'vrf_output': '[u8; 32]', 'vrf_proof': '[u8; 64]'}
# }

Example 2 

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pallet = metadata.get_metadata_pallet("Tokens")
storage_function = pallet.get_storage_function("TotalIssuance")

param_type_string = storage_function.get_params_type_string()
param_type_obj = runtime_config.create_scale_object(param_type_string[0])

type_info = param_type_obj.generate_type_decomposition()

print(type_info)
# [{
#   'Token': ('ACA', 'AUSD', 'DOT', 'LDOT', 'RENBTC', 'CASH', 'KAR', 'KUSD', 'KSM', 'LKSM', 'TAI', 'BNC', 'VSKSM', 'PHA', 'KINT', 'KBTC'), 
#   'DexShare': ({'Token': ('ACA', 'AUSD', 'DOT', 'LDOT', 'RENBTC', 'CASH', 'KAR', 'KUSD', 'KSM', 'LKSM', 'TAI', 'BNC', 'VSKSM', 'PHA', 'KINT', 'KBTC'), 'Erc20': '[u8; 20]', 'LiquidCrowdloan': 'u32', 'ForeignAsset': 'u16'}, {'Token': ('ACA', 'AUSD', 'DOT', 'LDOT', 'RENBTC', 'CASH', 'KAR', 'KUSD', 'KSM', 'LKSM', 'TAI', 'BNC', 'VSKSM', 'PHA', 'KINT', 'KBTC'), 'Erc20': '[u8; 20]', 'LiquidCrowdloan': 'u32', 'ForeignAsset': 'u16'}), 
#   'Erc20': '[u8; 20]', 
#   'StableAssetPoolToken': 'u32', 
#   'LiquidCrowdloan': 'u32', 
#   'ForeignAsset': 'u16'
# }]

In the above examples are simple value Enums representation as a tuple of possible values and complex Enums as a dict.

Examples (prior to MetadataV14)

Decode a SCALE-encoded Compact\<Balance>

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RuntimeConfiguration().update_type_registry(load_type_registry_preset("legacy"))
RuntimeConfiguration().update_type_registry(load_type_registry_preset("kusama"))
obj = RuntimeConfiguration().create_scale_object('Compact<Balance>', data=ScaleBytes("0x130080cd103d71bc22"))
obj.decode()
print(obj.value)

Encode to Compact\<Balance>

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RuntimeConfiguration().update_type_registry(load_type_registry_preset("legacy"))
obj = RuntimeConfiguration().create_scale_object('Compact<Balance>')
scale_data = obj.encode(2503000000000000000)
print(scale_data)

Encode to Vec\<Bytes>

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RuntimeConfiguration().update_type_registry(load_type_registry_preset("legacy"))
value = ['test', 'vec']
obj = RuntimeConfiguration().create_scale_object('Vec<Bytes>')
scale_data = obj.encode(value)
print(scale_data)

Add custom types to type registry

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RuntimeConfiguration().update_type_registry(load_type_registry_preset("legacy"))

custom_types = {
    "types": {
        "MyCustomType": "u32",
        "CustomNextAuthority": {
          "type": "struct",
          "type_mapping": [
             ["AuthorityId", "AuthorityId"],
             ["weight", "AuthorityWeight"]
          ]
        }
    }   
}

RuntimeConfiguration().update_type_registry(custom_types)

Or from a custom JSON file

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RuntimeConfiguration().update_type_registry(load_type_registry_preset("legacy"))
RuntimeConfiguration().update_type_registry(load_type_registry_file("/path/to/type_registry.json"))

Multiple runtime configurations

By default a singleton is used to maintain the configuration, for multiple instances: 

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# Kusama runtime config
runtime_config_kusama = RuntimeConfigurationObject()
runtime_config_kusama.update_type_registry(load_type_registry_preset("legacy"))
runtime_config_kusama.update_type_registry(load_type_registry_preset("kusama"))


# Polkadot runtime config
runtime_config_polkadot = RuntimeConfigurationObject()
runtime_config_polkadot.update_type_registry(load_type_registry_preset("legacy"))
runtime_config_polkadot.update_type_registry(load_type_registry_preset("polkadot"))

# Decode extrinsic using Kusama runtime configuration
extrinsic = runtime_config_kusama.create_scale_object(
    type_string='Extrinsic', 
    metadata=metadata_decoder
)
extrinsic.decode(ScaleBytes(extrinsic_data))