我想利用Combine框架进行并发API调用。这些API调用设置如下:
我的尝试:
- 首先,调用一个API获取帖子列表。
- 对于每个帖子,调用另一个API以获取评论。
我的尝试:
struct Post: Decodable {
let userId: Int
let id: Int
let title: String
let body: String
var comments: [Comment]?
}
struct Comment: Decodable {
let postId: Int
let id: Int
let name: String
let email: String
let body: String
}
class APIClient: ObservableObject {
@Published var posts = [Post]()
var cancellables = Set<AnyCancellable>()
init() {
getPosts()
}
func getPosts() {
let urlString = "https://jsonplaceholder.typicode.com/posts"
guard let url = URL(string: urlString) else {return}
URLSession.shared.dataTaskPublisher(for: url)
.receive(on: DispatchQueue.main)
.tryMap({ (data, response) -> Data in
guard
let response = response as? HTTPURLResponse,
response.statusCode >= 200 else {
throw URLError(.badServerResponse)
}
return data
})
.decode(type: [Post].self, decoder: JSONDecoder())
.sink { (completion) in
print("Posts completed: \(completion)")
} receiveValue: { (output) in
//Is there a way to chain getComments such that receiveValue would contain Comments??
output.forEach { (post) in
self.getComments(post: post)
}
}
.store(in: &cancellables)
}
func getComments(post: Post) {
let urlString = "https://jsonplaceholder.typicode.com/posts/\(post.id)/comments"
guard let url = URL(string: urlString) else {
return
}
URLSession.shared.dataTaskPublisher(for: url)
.receive(on: DispatchQueue.main)
.tryMap({ (data, response) -> Data in
guard
let response = response as? HTTPURLResponse,
response.statusCode >= 200 else {
throw URLError(.badServerResponse)
}
return data
})
.decode(type: [Comment].self, decoder: JSONDecoder())
.sink { (completion) in
print("Comments completed: \(completion)")
} receiveValue: { (output) in
print("Comment", output)
}
.store(in: &cancellables)
}
}
如何将getComments
链接到getPosts
,以便可以在getPosts
中接收评论输出?传统上,使用UIKit,我会使用DispatchGroup
来完成此任务。
请注意,我希望从APIClient仅接收一次发布事件的文章,以便SwiftUI视图只刷新一次。