小编Ana*_*ami的帖子

谁能解释它的mapping工作原理以及为什么使用它？像数组一样是项目的集合。我没有扎实的经验，我才刚刚开始。我在solidity官方文档页面上找到了此代码。

pragma solidity ^0.4.11;

Contract CrowdFunding {
// Defines a new type with two fields.
struct Funder {
    address addr;
    uint amount;
}

struct Campaign {
    address beneficiary;
    uint fundingGoal;
    uint numFunders;
    uint amount;
    mapping (uint => Funder) funders;
}

uint numCampaigns;
mapping (uint => Campaign) campaigns;

function newCampaign(address beneficiary, uint goal) returns (uint campaignID) {
    campaignID = numCampaigns++; // campaignID is return variable
    // Creates new struct and saves in storage. We leave out the mapping type. …