Parsing JSON response using Codable gives error in swift - ios

Question

I'm trying to parse JSON response using Codable but it gives me error.
I tried to refer from the below stack overflow link but did not work.
how do I parse Any in dictionary using swift
Below is my code, not sure where I'm wrong in this.
> enum JSONError: String,Error {
> case NoData = "ERROR: no data"
> case ConversionFailed = "ERROR: conversion from JSON failed"
> }
struct Owner : Decodable {
let full_name : String
let html_url:String
let follower:follower
}
struct follower : Decodable {
let followers_url : String
}
func jsonParser() {
let urlPath = "https://api.github.com/search/repositories?q=language:ruby&sort=stars&order=desc"
guard let endpoint = NSURL(string: urlPath) else {
print("Error creating endpoint")
return
}
let request = NSMutableURLRequest(url:endpoint as URL)
URLSession.shared.dataTask(with: request as URLRequest) { (data, response, error) in
do {
guard let data = data else {
throw JSONError.NoData
}
let jsonResponse = try JSONSerialization.jsonObject(with:
data)
let entries = try! JSONDecoder().decode([Owner].self, from: jsonResponse as! Data)
print(jsonResponse)
} catch let error as JSONError {
print(error.rawValue)
} catch let error as NSError {
print(error.debugDescription)
}
}.resume()
}
I need to get 3 information from this response - full name, html url and followers.
Link for web api
https://api.github.com/search/repositories?q=language:ruby
Please latest have a look at the code.
Below is the error message :
'__NSDictionaryI' (0x102965a98) to 'NSData' (0x102964580). 2019-02-09
16:17:42.062971+0530 PhotoViewwer[13342:259997] Could not cast value
of type '__NSDictionaryI' (0x102965a98) to 'NSData' (0x102964580).
Thanks

Answer 1

Please learn to read JSON. It's pretty easy. There are only two collection types, array ([]) and dictionary ({})
Your structs are wrong.
In the root dictionary of the JSON there is an array of dictionaries for key items.
In each dictionary there are keys full_name and owner (here is the location of the Owner struct).
A dictionary for key follower does not exist.
These structs represent the JSON correctly
struct Response : Decodable {
let items : [Item]
}
struct Item : Decodable {
let fullName : String
let owner : Owner
}
struct Owner : Decodable {
let htmlUrl : URL // URL strings can be decoded directly into URL
let followersUrl : URL
}
Add a completion handler to your function and use an enum as result type. The failure case returns all real errors. An URLRequest is redundant. Just pass the URL. The JSONSerialization line is pointless.
The convertFromSnakeCase strategy converts snake_cased keys to camelCased struct members
enum Result {
case success(Response), failure(Error)
}
func jsonParser(completion: #escaping (Result) -> Void) {
let endpoint = URL(string:"https://api.github.com/search/repositories?q=language:ruby&sort=stars&order=desc")!
URLSession.shared.dataTask(with: endpoint) { (data, response, error) in
if let error = error { completion(.failure(error)); return }
do {
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let entries = try decoder.decode(Response.self, from: data!)
completion(.success(entries))
} catch {
completion(.failure(error))
}
}.resume()
}
And call it
jsonParser { result in
switch result {
case .success(let entries) : print(entries)
case .failure(let error) : print(error)
}
}
Basically never use NS... classes if there are native equivalents, here URL for NSURL and URLRequest for NS(Mutable)URLRequest
Edit:
In Swift 5 the syntax becomes more convenient using the native Result type. It is able to convert the throwing expression
enum Result {
case success(Response), failure(Error)
}
func jsonParser(completion: #escaping (Result<Response,Error>) -> Void) {
let endpoint = URL(string:"https://api.github.com/search/repositories?q=language:ruby&sort=stars&order=desc")!
URLSession.shared.dataTask(with: endpoint) { (data, response, error) in
if let error = error { completion(.failure(error)); return }
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
completion(Result{ try decoder.decode(Response.self, from: data!) })
}.resume()
}

Answer 2

You need
func jsonParser() {
let urlPath = "https://api.github.com/search/repositories?q=language:ruby&sort=stars&order=desc"
guard let endpoint = NSURL(string: urlPath) else {
print("Error creating endpoint")
return
}
let request = NSMutableURLRequest(url:endpoint as URL)
URLSession.shared.dataTask(with: request as URLRequest) { (data, response, error) in
do {
let dec = JSONDecoder()
dec.keyDecodingStrategy = .convertFromSnakeCase
let entries = try dec.decode(Root.self, from:data!)
print(entries)
} catch {
print(error)
}
}.resume()
}
struct Root : Decodable {
let items:[Item]
}
struct Owner: Codable {
let login: String
let id: Int
let nodeId: String
let avatarUrl: String
let gravatarId: String
let url, htmlUrl, followersUrl: String
let followingUrl, gistsUrl, starredUrl: String
let subscriptionsUrl, organizationsUrl, reposUrl: String
let eventsUrl: String
}
struct Item: Codable {
let fullName : String
let htmlUrl:String
let owner: Owner
}
You shouldn't cast the response to data here
from: jsonResponse as! Data)
as it will crash