Try to parsing json into class object fail - json

Question

I need help to parsing the json using Swift . I could not parse them into an array of a class object using swift. What I tried is I bundle the json key value into an array of object and return. However, I could not deal with the types. It so confuse.
Could someone help me.
The json I have:
{
"mass_info1":
[{
"mass_id":7780,
"mass_date":"5/1/2019",
"mass_time":"7:30 PM",
"mass_location":"",
"mass_description": “Blah1”
} ] ,
"mass_info2":
[ {
"mass_id":7781,
"mass_date":"6/10/2019",
"mass_time":"7:30 PM",
"mass_location”:”1234 some place Los Angeles”,
"mass_description": “blah2”
} ] ,
"mass_info3":
[ {
"mass_id":7783,
"mass_date":"5/21/2019",
"mass_time":"7:30 PM",
"mass_location":"",
"mass_description": “blah3”
} ] ,
"mass_info4":
[ {
"mass_id":1115,
"mass_date":"4/5/2019",
"mass_time":"2:30 PM",
"mass_location":"4050 Mission Ave, Oceanside, CA 92057",
"mass_description": “blah4”
} ]
}
The class MassInfoObject import Foundation
struct MassInfoObject {
var mass_id:Int
var mass_date: String?
var mass_time:String?
var mass_location:String?
var mass_description:String?
init(mass_id:Int,mass_date:String,
mass_time:String,mass_location:String,mass_description:String)
{
self.mass_id=mass_id
self.mass_date=mass_date
self.mass_time=mass_time
self.mass_location=mass_location
self.mass_description=mass_description
}
}
and the code that I get the json from a URLSession.
func getjson()->[MassInfoObject]? {
let urlPath = "http://myclassinfo.com/dev/json.php"
let url = URL(string: urlPath)
var massObjArray = [MassInfoObject]()
var index:Int = 0
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
print("Task completed")
guard data != nil && error == nil else {
//print(error?.localizedDescription)
return
}
do {
if let jsonResult = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary {
for (key, value) in jsonResult {
//print("Value: \(value) for key: \(key)")
if let results = jsonResult[key] as? [String]
{
let dict = results[index].toJSON() as? [String:AnyObject] // can be any type here
for (key,value) in dict!{
let result2 = dict![key] as! String
print (result2)
}
}
}
}
} catch let parseError as NSError {
print("JSON Error \(parseError.localizedDescription)")
}
}
task.resume()
return massObjArray
}

Answer 1

The json you are trying to parse does not have a very logical structure. If you have control over the json, you should work on that first. If you don't have control I suggest converting the json on your client end before parsing.
The following works in a Playground:
let str = """
{ "mass_info1": [{ "mass_id":7780, "mass_date":"5/1/2019", "mass_time":"7:30 PM", "mass_location":"", "mass_description": "Blah1"
} ] ,
"mass_info2": [ { "mass_id":7781, "mass_date":"6/10/2019", "mass_time":"7:30 PM", "mass_location":"1234 some place Los Angeles", "mass_description": "Blah2"
} ] ,
"mass_info3":
[ { "mass_id":7783, "mass_date":"5/21/2019", "mass_time":"7:30 PM", "mass_location":"", "mass_description": "blah3"
} ] ,
"mass_info4":
[ { "mass_id":1115, "mass_date":"4/5/2019", "mass_time":"2:30 PM", "mass_location":"4050 Mission Ave, Oceanside, CA 92057", "mass_description": "blah4"
} ]
}
"""
struct MassInfoObject: Codable {
var mass_id: Int
var mass_date: String?
var mass_time: String?
var mass_location: String?
var mass_description: String?
}
let data = str.data(using: .utf8)!
let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: [[String: Any]]]
let jsonArray = json!.values.map { $0 }
let cleanedJson = try JSONSerialization.data(withJSONObject: jsonArray, options: [])
let decoder = JSONDecoder()
let items = try decoder.decode([[MassInfoObject]].self, from: cleanedJson)
The first steps are to convert the json to something that can be parsed easily. Because now MassInfoObject conforms to Codable, you can use a simple JSONDecoder to decode an array of objects, this is just one line of code.
Also, in your networking code you are calling an async task, but your are returning immediately, that's not going to work. When you return from the getJson function, you don't have the results yet. The easiest thing to do is use a closure that you can call with the results:
In your networking code it would look as such:
func getjson(handler: #escaping ([MassInfoObject]?)->()) {
let urlPath = "http://myclassinfo.com/dev/json.php"
let url = URL(string: urlPath)
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
print("Task completed")
guard let data = data && error == nil else {
//print(error?.localizedDescription)
return
}
do {
let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: [[String: Any]]]
let jsonArray = json!.values.map { $0 }
let cleanedJson = try JSONSerialization.data(withJSONObject: jsonArray, options: [])
let decoder = JSONDecoder()
let items = try decoder.decode([[MassInfoObject]].self, from: cleanedJson).compactMap { $0 }
handler(items)
} catch let parseError as NSError {
print("JSON Error \(parseError.localizedDescription)")
handler(nil)
}
}
task.resume()
}
If you have json that looks like this:
[
{
"mass_description": "Blah1",
"mass_date": "5/1/2019",
"mass_location": "",
"mass_time": "7:30 PM",
"mass_id": 7780
},
{
"mass_description": "blah2",
"mass_date": "6/10/2019",
"mass_location": "1234 some place Los Angeles",
"mass_time": "7:30 PM",
"mass_id": 7781
},
{
"mass_description": "blah3",
"mass_date": "5/21/2019",
"mass_location": "",
"mass_time": "7:30 PM",
"mass_id": 7783
},
{
"mass_description": "blah4",
"mass_date": "4/5/2019",
"mass_location": "4050 Mission Ave, Oceanside, CA 92057",
"mass_time": "2:30 PM",
"mass_id": 1115
}
]
You could easily decode this:
let items = try JSONDecoder().decode([MassInfoObject].self, data)

Answer 2

Thank Marcel, and everyone who helped me. Here is the code that I used
struct MassObj:Decodable{
var mass_id:Int
var mass_date: String
var mass_time:String
var mass_location:String
var mass_description:String
}
func getJsonArray2() {
let urlPath = "http://myclassinfo.com/dev/json.php"
guard let url = URL(string: urlPath) else {return }
let task = URLSession.shared.dataTask(with: url)
{
data, response, error in
print("Task completed")
guard data != nil && error == nil else {
//print(error?.localizedDescription)
return
}
do{
var massArray = [MassObj]()
massArray = try JSONDecoder().decode([MassObj].self, from:data!)
for object in massArray {
print("\(object.mass_id) == \(object.mass_date) == \(object.mass_description)")
}
}catch let jerr {
print(jerr)
}
}
task.resume()
}
================
and the json is
[
{
"mass_description": "Blah1",
"mass_date": "5/1/2019",
"mass_location": "",
"mass_time": "7:30 PM",
"mass_id": 7780
},
{
"mass_description": "blah2",
"mass_date": "6/10/2019",
"mass_location": "1234 some place Los Angeles",
"mass_time": "7:30 PM",
"mass_id": 7781
},
{
"mass_description": "blah3",
"mass_date": "5/21/2019",
"mass_location": "",
"mass_time": "7:30 PM",
"mass_id": 7783
},
{
"mass_description": "blah4",
"mass_date": "4/5/2019",
"mass_location": "4050 Mission Ave, Oceanside, CA 92057",
"mass_time": "2:30 PM",
"mass_id": 1115
}
]