【開發智能合約 — Solidity系列】實作篇Ep.7 — 狀態的可變性限制(State Mutability)

pure

contract Example {

    string private state  = "start";    function pureFunc(uint a, uint b) public pure returns(uint) {

        // ❌ 無法讀取狀態

        // assert(bytes(state).length > 0);

        // ❌ 無法修改狀態

        // state = "doing";

        return a + b;

    }

}

view

contract Example {

    string private state  = "start";    function viewFunc(uint a, uint b) public view returns(uint) {

        // ✔️ 可以讀取狀態

        assert(bytes(state).length > 0);

        // ❌ 無法修改狀態

        // state = "doing";

        return a + b;

    }

}

none

function func(uint a, uint b) public returns(uint) {

        // ✔️ 可以讀取狀態

        assert(bytes(state).length > 0);

        // ✔️ 無法修改狀態

        state = "doing";

        return a + b;

 }

結語