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Contract Data Structure

Last Updated: Sep 05, 2019

Basic data types

The contract platform of Ant Blockchain supports almost all data types in Solidity. However, some user-defined input parameter types are not supported, for example, the two-dimensional arrays. The contract platform also provides the identity type that contains a 32-byte string to identify each user. The address type in Solidity is not supported.

We recommend that you use the following data types:

Type Sample Supported by the contract platform Supported as an input parameter
bool bool a = true Yes Yes
uint uint a = 1 Yes Yes
uint8 ~ uint256 uint8 a = 1 Yes Yes
int int a = 1 Yes Yes
int8 ~ int256 int8 a = 1 Yes Yes
bytes bytes a = “test” Yes Yes
bytes1 ~ bytes32 bytes1 a = “a” Yes Yes
string string a = “test” Yes Yes
identity identity id = 0x1234567890123456789012345678901234567890123456789012345678901234567890000 Yes Yes
int[] int256[] a = [1,2,3,4,5] Yes Yes
uint[] uint256[] a = [1,2,3,4,5] Yes Yes
bytes1[] ~ bytes32[] bytes4[] asd = new bytes4; Yes Yes
string[] string[] a = [“adbc”,”dg”] Yes No
enum enum a {a,b,c} Yes No
struct struct a { string name;} Yes No


  • These data types are used within the contract.
  • Input parameters: The parameters passed in when a method is called on the client.

For example, in the issuance methods of the credit management contract, the identity type and the int256 type are both input parameter types and supported by the contract platform.

  1. function Issue(identity account, int256 value)

The mapping declaration type corresponding to the user credits and the account ID can be used within a contract. However, the mapping declaration type cannot be used as an input type for a function. For example:

  1. function example(mapping(identity=>int256) map) // An error occurred. The mapping declaration type is not supported as an input type.

Other types

Solidity also supports other data types, including:

  • mapping
  • struct
  • Units of time: seconds, minutes, hours, days, weeks, and years.

For more information, see Data types supported in Solidity (English).