问题
I'm trying to retrieve some JSON data from a URL, however it is returning 0 bytes every time in the data. I've checked several different SO posts, and none seem to match the exact problem I am having as the server I am getting data from indeed uses HTTPS with TLS 1.2. So I don't think there's anything I need to add to my info.plist, though I could be wrong.
Here is my code:
var tournaments: [Tournament] = []
/// Base API URL
let baseURL: String = "https://www.burningmeter.com/tournaments.json?page=1"
// ...
func retrieveAPIData() {
// Build the API string
var request: URLRequest = URLRequest(url: URL(string: baseURL)!)
request.cachePolicy = URLRequest.CachePolicy.reloadIgnoringLocalCacheData
request.addValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")
request.httpMethod = "GET"
// Request the data
let session: URLSession = URLSession.shared
let task = session.dataTask(with: request) { (data, response, error) in
// Did we get an error?
guard error == nil else {
print(error!)
return
}
guard let json = data else {
print("No data")
return
}
guard json.count == 0 else {
print("Zero bytes of data")
return
}
let jsonDecoder = JSONDecoder()
let tournaments = try! jsonDecoder.decode(TournamentPage.self, from: json)
// We got our values, let's go
self.tournaments = tournaments.tournaments
}
task.resume()
}
Tournament structure:
struct Tournament : Codable {
let id: Int
let name: String
let game_id: Int
let game_iteration_id: Int
let state: Int
let starts_at: String
let creator_id: Int
let stream_url: String
let entrant_count: Int
let prereg_count: Int
let path: String
}
struct TournamentPage : Codable {
let page: Int?
let results_per_page: String
let tournament_count: Int
let tournaments: [Tournament]
}
回答1:
You have a mistake in guard statement. You wrote == instead of != in json.count == 0. It should be like in the code below:
guard json.count != 0 else {
print("Zero bytes of data")
return
}
Tested in the playground with the following code (Removed Encoder):
let baseURL: String = "https://www.burningmeter.com/tournaments.json?page=1"
func retrieveAPIData() {
var request: URLRequest = URLRequest(url: URL(string: baseURL)!)
request.cachePolicy = URLRequest.CachePolicy.reloadIgnoringLocalCacheData
request.addValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")
request.httpMethod = "GET"
// Request the data
let session: URLSession = URLSession.shared
let task = session.dataTask(with: request) { (data, response, error) in
print(data!.count)
print(response)
// Did we get an error?
guard error == nil else {
print(error!)
return
}
guard let json = data else {
print("No data")
return
}
guard json.count != 0 else {
print("Zero bytes of data")
return
}
print(String(decoding: json, as: UTF8.self))
}
task.resume()
}
retrieveAPIData()
Printed result:
8031
Optional(<NSHTTPURLResponse: 0x7fbce1650fc0> { URL: https://www.burningmeter.com/tournaments.json?page=1 } { Status Code: 200, Headers {
"Access-Control-Allow-Origin" = (
"*"
);
"Cache-Control" = (
"max-age=0, private, must-revalidate"
);
Connection = (
"keep-alive"
);
"Content-Type" = (
"application/json; charset=utf-8"
);
Date = (
"Thu, 08 Nov 2018 15:40:40 GMT"
);
Etag = (
"W/\"5d5a17c8ff6f705d6bb56c6ed8b6a099\""
);
Server = (
Cowboy
);
"Strict-Transport-Security" = (
"max-age=31536000"
);
"Transfer-Encoding" = (
Identity
);
Via = (
"1.1 vegur"
);
"X-Content-Type-Options" = (
nosniff
);
"X-Frame-Options" = (
SAMEORIGIN
);
"X-Request-Id" = (
"0d7f8ae9-92d2-41d8-8678-6c9b2bdb5e3b"
);
"X-Runtime" = (
"0.044064"
);
"X-Xss-Protection" = (
"1; mode=block"
);
} })
JSON result:
{
"page": "1",
"results_per_page": "50",
"tournament_count": 33,
"tournaments": [{
"id": 1872,
"name": "Pinup Biweekly - Nov 1",
"game_id": 90,
"game_iteration_id": 133,
"state": 30,
"starts_at": "2018-11-02T00:00:00.000Z",
"creator_id": 960,
"stream_url": null,
"entrant_count": 6,
"prereg_count": 0,
"path": "/t/1872/pinup-biweekly-nov-1"
}, {
"id": 1874,
"name": "IBTY #45",
"game_id": 21,
"game_iteration_id": 38,
"state": 30,
"starts_at": "2018-11-02T22:03:00.000Z",
"creator_id": 185,
"stream_url": null,
"entrant_count": 11,
"prereg_count": 0,
"path": "/t/1874/ibty-45"
}, {
"id": 1875,
"name": "SFV Weekly 11/2/18",
"game_id": 6,
"game_iteration_id": 14,
"state": 30,
"starts_at": "2018-11-03T00:55:00.000Z",
"creator_id": 957,
"stream_url": null,
"entrant_count": 9,
"prereg_count": 0,
"path": "/t/1875/sfv-weekly-11-2-18"
}, {
"id": 1876,
"name": "Weekly SC6 11/2/18",
"game_id": 106,
"game_iteration_id": 149,
"state": 20,
"starts_at": "2018-11-03T01:04:00.000Z",
"creator_id": 957,
"stream_url": null,
"entrant_count": 6,
"prereg_count": 0,
"path": "/t/1876/weekly-sc6-11-2-18"
}, {
"id": 1879,
"name": "UNIST - WS 11/3",
"game_id": 12,
"game_iteration_id": 23,
"state": 30,
"starts_at": "2018-11-03T18:30:00.000Z",
"creator_id": 949,
"stream_url": null,
"entrant_count": 8,
"prereg_count": 0,
"path": "/t/1879/unist-ws-11-3"
}, {
"id": 1881,
"name": "DBFZ - WS 11/3",
"game_id": 86,
"game_iteration_id": 129,
"state": 30,
"starts_at": "2018-11-03T18:30:00.000Z",
"creator_id": 949,
"stream_url": null,
"entrant_count": 8,
"prereg_count": 0,
"path": "/t/1881/dbfz-ws-11-3"
}, {
"id": 1882,
"name": "SFV - WS 11/3",
"game_id": 6,
"game_iteration_id": 14,
// more
}
// More output here
}
Received length is 8031
来源：https://stackoverflow.com/questions/53210721/0-bytes-of-data-from-https-urlsession-datatask