How to compare two JSON objects in Swift? - ios

Question

I have an json object and store it as initialData and after some changes in store the json object into another modifiedData. Now I am trying to compare two json object of initialData and modifiedData but i could not able to compare it.
Note: Here json object are dynamic value.
Sample code:
let jsonObjectVal = JSON(message.body)
let initialData = jsonObjectVal
In save action i have modifiedData object.
let jsonObjectModVal = JSON(message.body)
let modifiedData = jsonObjectModVal
if initialFormDataJson == jsonObjectVal {
print("json object are equal save handler")
} else {
print("json object are not equal save handler")
}
Any help much appreciated pls...

Answer 1

Here's an example with a random data structure on how exactly you can do it:
import Foundation
final class YourObject: Decodable, Equatable {
var field1: String
var field2: Int
var field3: [String : Double]
static func == (lhs: YourObject, rhs: YourObject) -> Bool {
lhs.field1 == rhs.field1
&& lhs.field2 == rhs.field2
&& lhs.field3 == rhs.field3
}
}
let firstJSONString = """
{
"field1":"Some string",
"field2":1,
"field3":{
"Some string":2
}
}
"""
let firstJSONData = firstJSONString.data(using: .utf8)!
let firstObject = try? JSONDecoder().decode(YourObject.self, from: firstJSONData)
let secondJSONString = """
{
"field1":"Some string",
"field2":1,
"field3":{
"Some string":2
}
}
""" // Same.
let secondJSONData = secondJSONString.data(using: .utf8)!
let secondObject = try? JSONDecoder().decode(YourObject.self, from: secondJSONData)
let thirdJSONString = """
{
"field1":"Some other string",
"field2":2,
"field3":{
"Some string":3
}
}
""" // Differs.
let thirdJSONData = thirdJSONString.data(using: .utf8)!
let thirdObject = try? JSONDecoder().decode(YourObject.self, from: thirdJSONData)
print(firstObject == secondObject) // true
print(firstObject == thirdObject) // false
Note: You mentioned that the object should be dynamic, that's why it's a class. If you needed a value object, you would be able to use struct and avoid manual implementation of the ==operator.
It's just a start of course. Having a specific JSON structure in your hands you can always search for more complicated examples, internet swarms with them.

Answer 2

Create a NSObject class or struct from the JSON and compare all the properties to check for equality and return true/false accordingly.
Equatable protocol will come in handy here.
class A: Equatable {
func equalTo(rhs: A) -> Bool {
// whatever equality means for two As
}
}
func ==(lhs: A, rhs: A) -> Bool {
return lhs.equalTo(rhs)
}

Answer 3

If you want to compare two completely arbitrary JSON objects (e.g. for unit testing), I'd suggest using the GenericJSON library. Add it to your project and/or Package.swift, and then (borrowing from #lazarevzubov's answer):
import GenericJSON
// Assume `YourObject` is `Encodable`
let testObject = YourObject(field1: "Some string", field2: 1, field3: ["Some string": 2])
let expectedData = """
{
"field1":"Some string",
"field2":1,
"field3":{
"Some string":2
}
}
""".data(using: .utf8)!
let expectedJSON = try? JSON(JSONSerialization.jsonObject(with: expectedData))
let actualJSON = try? JSON(encodable: testObject)
XCTAssertEqual(actualJSON, expectedJSON, "JSON should be equal")
A nice bonus is that you don't need to add any otherwise unnecessary Decodable or Equatable conformance to your model objects.

Answer 4

For Compare 2 objects use === operator
for eg.
let jsonObjectModVal = JSON(message.body)
let modifiedData = jsonObjectModVal
if initialFormDataJson === jsonObjectVal {
print("json object are equal save handler")
} else {
print("json object are not equal save handler")
}