How to change the value of a property of all the instances of a class?

Question

I have a Student Class and a Uniform Class. When an Student instance is created, the student will have a uniform with Green Color.

class Student{
    var uniform = Uniform.uniformColor
}

class Uniform{
    static var uniformColor = "Green"
        {
        didSet(newColor){
            print("Change to \(newColor)")

        }
    }

}



let student1 = Student()
let student2 = Student()

print(student1)
print(student2)

Uniform.uniformColor = "Red"

print(Uniform.uniformColor)

print(student1.uniform)
//print Green
print(student2.uniform)
//print Green
let student3 = Student()
print(student3.uniform)
//print Red

How do I set the colour of the uniform of all the students, to Red at once?

Answer 1

You could try to create an array of students, add each student to it. Next iterate with for-loop over all students and assign a Red color to Uniform.

Answer 2

If you always want a student to have the latest Uniform.uniformColor , then change uniform to a computed property:

class Student {
    var uniform: String { return Uniform.uniformColor }
}

Example:

let student1 = Student()
let student2 = Student()

print(student1.uniform)  // Green
print(student2.uniform)  // Green

Uniform.uniformColor = "Red"

print(student1.uniform)  // Red
print(student2.uniform)  // Red

Answer 3

Why not declare the color of Uniform as instance property and create a default initializer which always creates an Uniform with red color in the Student class?

class Student 
{  
  let uniform : Uniform

  init() {
    self.uniform = Uniform(color:"Red")
  }
}

class Uniform
{
  var color = "Green" {
    didSet(newColor){
      print("Change to \(newColor)")
    }
  }

  init(color : String) {
    self.color = color
  }
}

let student = Student()
print(student.uniform.color) // "Red"

Answer 4

var students = [Student]()
students.append(student1)
students.append(student2)
for student in students {
    student.uniform.uniformColor = "Red"
}