调用另一个合约中的函数 - Solidity

我需要使用 Truffle 调用另一个合约中的函数。这是我的合同样本：

类别.sol:

contract Category {
  /// ...
  /// @notice Check if category exists
  function isCategoryExists(uint256 index) external view returns (bool) {
    if (categories[index].isExist) {
      return true;
    }
    return false;
  }
}

帖子.sol:

contract Post {
  /// ...
  /// @notice Create a post
  function createPost(PostInputStruct memory _input)
    external
    onlyValidInput(_input)
    returns (bool)
  {
    /// NEED TO CHECK IF CATEGORY EXISTS
    /// isCategoryExists() <<<from Category.sol>>>
  }
}

部署.js

const Category = artifacts.require("Category");
const Post = artifacts.require("Post");

module.exports = function (deployer) {
  deployer.deploy(Category);
  deployer.deploy(Post);
};

我能做些什么？

您可以从其他合同继承。假设您想从邮政合同导入。

contract Category is Post {
  /// ...
  /// @notice Check if category exists
  function isCategoryExists(uint256 index) external view returns (bool) {
    if (categories[index].isExist) {
      return true;
    }
    return false;
  }
  // you can call createPost
  createPost(){}
}