Solidity uses mapping+struct complex data structure

When using the complex data structure of mapping+struct in solidity, the problem encountered is "Mappings cannot be assigned to".

More blockchain technology and application classification:

Blockchain applicationBlockchain     development

Ethernet Square | Fabric | BCOS | cryptography | consensus algorithm | bitcoin |  Other chain

Token Economy |  Traditional Financial Scenarios | Decentralized Finance | Anti-counterfeiting Traceability | Data Sharing | Trusted Deposit

Error code

Code

constructor() public{
  dataBases[TypeConvertUtil.stringToBytes32(TABLE_BAG_NAME)] = bagRecordOf;
  dataBases[TypeConvertUtil.stringToBytes32(TABLE_LOCATIONS_NAME)] = locationRecordOf;
  dataBases[TypeConvertUtil.stringToBytes32(TABLE_ATTENDLOCATION_NAME)] = attendLocationRecordOf;
}

Writing in this way will cause the following error:

browser/TableDefTools.sol:112:9: TypeError: Mappings cannot be assigned to.
dataBases[TypeConvertUtil.stringToBytes32(TABLE_BAG_NAME)] = bagRecordOf;
^----------------------------------------------------------------------^

Correct code

Define the structure:

struct RecordBean {
	// 表名称
	string tableName;
	// 主键值
	string primaryKey;
	// 内容值
	string[] values;
}
mapping(bytes32 => mapping(bytes32 => RecordBean)) dataBases;

Assignment:

dataBases[TypeConvertUtil.stringToBytes32(_tableName)][TypeConvertUtil.stringToBytes32(_primaryKey)] = recordBean;

Value:

RecordBean recordBean = dataBases[TypeConvertUtil.stringToBytes32(_tableName)][TypeConvertUtil.stringToBytes32(_primaryKey)];

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Original link: Solidity uses mapping+struct complex data structure