iterate over object class attributes in Swift

Question

Is there a Simple way in Swift to iterate over the attributes of a class.

i.e. i have a class Person, and it has 3 attributes: name, lastname, age.

is there something like

for attribute in Person {
     println("\(attribute): \(attribute.value)")
}

the output would be for example:

name: Bob
lastname: Max
age: 20

Answer 1

They have removed reflect within Swift 2.0. This is how I am enumerating attributes and values.

class People {
    var name = ""
    var last_name = ""
    var age = 0
}

var user = People()
user.name  = "user name"
user.last_name = "user lastname"
user.age = 20

let mirrored_object = Mirror(reflecting: user)

// Swift 2
for (index, attr) in mirrored_object.children.enumerate() {
    if let property_name = attr.label as String! {
        print("Attr \(index): \(property_name) = \(attr.value)")
    }
}

// Swift 3 and later
for (index, attr) in mirrored_object.children.enumerated() {
    if let property_name = attr.label as String! {
        print("Attr \(index): \(property_name) = \(attr.value)")
    }
}

Output:
Attr 0: name = user name
Attr 1: last_name = user lastname
Attr 2: age = 20

Answer 2

Yes, if you just need to print properties of a struct or class, and the properties are simple types like String and Int, you can use reflect and MirrorType.

func print_properties(mirror: MirrorType) {
    for i in 0..<mirror.count {
        let (name, childMirror) = mirror[i]
        let value = childMirror.value
        println("\(i): \(name) = \(value)")
    }
}

struct Person {
    let first_name: String
    let last_name: String
    let age: Int
}

let john = Person(first_name:"John", last_name:"Doe", age:27)
let mirror = reflect(john)
print_properties(mirror)

If you have nested structs, enums, you need to do a bit more work.

Answer 3

As @mohacs suggested, You can provide a function Description in your required class like follows;

func description() -> String{

        let mirrored_object = Mirror(reflecting: self)
        let str:NSMutableString = NSMutableString()
        for (index, attr) in mirrored_object.children.enumerated() {
            if let property_name = attr.label as String! {
                str.append(" Attr \(index): \(property_name) = \(attr.value)")
            }
        }
        //print("desc=\(str)")
        return str as String
    }

Then simple call this instance method

  let jsonOb:JsonModel = self.ObjArray[Index]
  print("jsonOb = \(jsonOb.description())")

Answer 4

Apple didn't remove reflect,they just change it to _reflect,they also changed MirrorType to _MirrorType.
The Swift 2.0 version of @Teemu Kurppa 's code:

func print_properties(mirror: _MirrorType) {
  for i in 0..<mirror.count {
    let (name, childMirror) = mirror[i]
    let value = childMirror.value
    print("\(i): \(name) = \(value) ")
  }
}

struct Person {
    let first_name: String
    let last_name: String
    let age: Int
}

let john = Person(first_name:"John", last_name:"Doe", age:27)
let mirror = _reflect(john)
print_properties(mirror)

Answer 5

Here's Swift 5 version of object description:

class TestClass: CustomStringConvertible {

    public var description: String {
        return Mirror(reflecting: self).children.compactMap({
            if let label = $0.label {
                return "\(label): \($0.value)"
            }
            
            return ""
        }).joined(separator: "\n")
    }
}