How to call struct using string value in swift 4 - swift

Question

JSON
{
"method" : 105,
"values" : {
"item_image" : "A123",
"name" : "Image1",
"description" : "Sample Description"
},
"columns" : {
"name" : {
"type" : "text",
"source" : "name"
},
"item_image" : {
"type" : "image",
"source" : "item_image"
},
"description" : {
"type" : "text",
"source" : "description"
}
}
}
Model
struct Params:Decodable {
let values: Values
let columns: [String: Columns]
}
struct Columns: Decodable {
let source: String
let type: String
}
struct Values: Decodable {
let name: String
let item_image: String
let description: String
}
Code
for (_, val) in param.columns {
colType = val.type
colSource += ", \(val.source)"
let s = "param.values.\(val.source)" \\this line is invalid
let vals = s
print("value: ",vals)
}
Hi! Im working with the lines of code above, and I'm having a problem to call my struct. Instead of using static values i want it dynamic with the code below but its invalid:
let s = "param.values.\(val.source)"
invalid because when it comes to this line:
let vals = s
the result is param.values.name or param.values.item_image, my expected value is Image1 or A123.
to make it clear here's the expected value from the codes and how can I achieve this:
for (_, val) in param.columns {
colType = val.type! expectedvalue= text
colSource += ", \(val.source)" expectedvalue= ", name, item_image, description"
let s = "param.values.\(val.source)" expectedvalue: "param.values.name" or "param.values.item_image"
let vals = s expectedvalue: Image1 or A123
print("value: ",vals) expectedvalue: value: Image1
}
Thanks!

Answer 1

I don't think you can access a property by string. One solution could be to create a mapper function that actually handles that. Still, this assumes that you have pre-determined keys.
struct Params:Decodable {
let values: Values
let columns: [String: Columns]
func getValues(from columns: Columns) -> String? {
switch columns.source {
case "item_image":
return values.item_image
case "name":
return values.name
case "description":
return values.description
default:()
}
if columns.source == "item_image" {
return values.item_image
}
return nil
}
}
struct Columns: Decodable {
let source: String
let type: String
}
struct Values: Decodable {
let name: String
let item_image: String
let description: String
}
let column = Columns(source: "name", type: "text")
let column2 = Columns(source: "item_image", type: "image")
let column3 = Columns(source: "description", type: "text")
let values = Values(name: "Image1", item_image: "A123", description: "Sample Description")
let params = Params(values: values, columns: ["name": column, "item_image": column2, "description": column3])
let name = params.getValues(from: column) //Image1
let itemImage = params.getValues(from: column2) //A123
let description = params.getValues(from: column3) //Sample Description