How to parse json correctly in ios? - ios

Question

For example I need to get all english "text" values of "ex" scope from JSON example
What I do:
let result = json["def"].arrayValue.map({ $0["tr"].arrayValue.map { $0["ex"] } })
but at as a result I got a double massive and if I intend to get all "text" then I will get a triple array. Guess should be another more elegant approach to this task. Is anyone can show a really good solution?

Answer 1

If your expression gives 3 arrays of Strings you could add .reduce([], +) at the end to join the 3 arrays into
one.
EDIT:
I was typing from memory, and said the wrong thing. You would use reduce, not joined.
let result = json["def"]
.arrayValue
.map({ $0["tr"].arrayValue.map { $0["ex"] } })
.reduce([], +)
That should give you what you want.
EDIT #2:
The reduce function operates on sequences (like arrays). It takes an "initial result" value that seeds the process, and then a closure that operates on 2 elements, and returns a result. (a "binary" closure)
The + operator is actually a binary closure in Swift. It takes 2 elements and returns a single result, so you can simply pass in + instead of a closure. For arrays, + returns the result of combining the arrays.
So when you use reduce() on an array of arrays, and [] as the initial result, it combines [] with the first array, then the result of each + operator with the next entry in the array.
Take this simplified code for example:
//Start with an array of arrays of strings
let arrays = [
["string1", "string2", "string3"],
["string4", "string5", "string6"],
["string7", "string8", "string9"]
]
//First loop through the outer arrays and log their contents
for (index, object) in arrays.enumerated() {
print("array[\(index)] = \(object)")
}
//Now combine the outer arrays into a single array
let combined = arrays.reduce([], + )
//Now print the entries in the combined array
print("\n---- combined arrays ----")
for (index, object) in combined.enumerated() {
print("array[\(index)] = \(object)")
}
That produces the following output:
array[0] = ["string1", "string2", "string3"]
array[1] = ["string4", "string5", "string6"]
array[2] = ["string7", "string8", "string9"]
---- combined arrays ----
array[0] = string1
array[1] = string2
array[2] = string3
array[3] = string4
array[4] = string5
array[5] = string6
array[6] = string7
array[7] = string8
array[8] = string9