使用Combine的Zip操作符合并两个返回Result<T, Error>的API请求如何优化？

优化实现方案 #

你可以直接利用Result自带的get()方法简化取值逻辑，同时把Result解析逻辑提前放到Combine操作链中处理，不需要在sink闭包内手动写switch匹配。优化后的代码如下：

// 提前解析两个Publisher的Result，错误直接在流中处理完成
let postsStream = getPosts()
    .map { result -> [Post] in
        do {
            return try result.get()
        } catch {
            print("Error: \(error.localizedDescription)")
            return []
        }
    }

let usersStream = getUsers()
    .map { result -> [User] in
        do {
            return try result.get()
        } catch {
            print("Error: \(error.localizedDescription)")
            return []
        }
    }

Publishers.Zip(postsStream, usersStream)
    .map { posts, users -> [ForumPost] in
        // 用字典映射优化匹配效率，避免双重循环
        let userMapping = users.reduce(into: [Int: String]()) { $0[$1.id] = $1.username }
        return posts.compactMap { post in
            guard let username = userMapping[post.userId] else { return nil }
            return ForumPost(username: username, title: post.title)
        }
    }
    .sink(receiveValue: { [weak self] forumPosts in
        guard let self = self else { return }
        print(forumPosts)
        // 最终结果处理，比如UI赋值、数据存储等
    })
    .store(in: &publishers)

额外优化建议 #

如果项目中这类Result类型的Publisher比较多，可以写个扩展复用解析逻辑，进一步简化代码：

extension Publisher where Failure == Never {
    func resolveResult<T>(printError: Bool = true) -> AnyPublisher<[T], Never> where Output == Result<[T], Error> {
        map { result in
            do {
                return try result.get()
            } catch {
                if printError {
                    print("Error: \(error.localizedDescription)")
                }
                return []
            }
        }
        .eraseToAnyPublisher()
    }
}

使用扩展后，两个流的解析代码可以简化为：

let postsStream = getPosts().resolveResult()
let usersStream = getUsers().resolveResult()

内容的提问来源于stack exchange，提问作者Wazza