solidity-cheat-sheet.md

Solidity Cheat Sheet

Data Types

Solidity is statically typed: each variable type needs to be needs to be specified (or coeracible, see Type Dedication below)

• bool: boolean, expects outcome to be true/false

• int / uint: signed and unsigned integers. Unsigned integers are always positive numbers. Keywords uint8 through uint256 increment in steps of 8 bits. Same applies to int (int8 through int256). uint & int are aliases for uint256 & int256 respectively.

• fixed / ufixed: Not fully supported in solidity yet. Keywords ufixedMxN/fixedMxN where M is # of bits taken by type & N is # of decimal points. M can range from 8 - 256 in increments of 8. N is between 0 & 80, inclusive. ufixed/fixed are aliases for ufixed128x19 & fixed128x19, respectively.

• address: 20 byte value (the size of an Eth address). Address types also have members and serve as the base for all contracts.

  • <address>.balance (uint256): balance of address in Wei
  • <address>.transfer(uint256 amount): send given amount of Wei to address, throws on failure
  • <address>.send(uint256 amount) returns (bool): sends given amount of Wei to address, returns false on failure.
    • generally use pattern where recipient withdraws money instead of using send.
  • there are 3 additional modifiers on address: call, delegatecall and callcode are very low-level functions and should only be used as a last resort as they break the type-safety of Solidity. More details...
  • All contracts inherit the members of address, so it is possible to query the balance of the current contract using this.balance.

• fixed-size byte arrays: bytes1, bytes2,bytes3, ..., bytes32. .length gives fixed length of byte array (read-only)

• dynamically sized byte array.