How to conform to a protocol's variables' set & get?

Question

I\'m playing around with protocols and how to conform to them.

protocol Human {    
    var height: Int { get set }    
}

struct Boy: Human { 
    var height: In         


        

Answer 1

Prerequisite:

Go into your playground and just write the snippet below:

var height: Int {
    get {
        return 5
    }
}    

or similarly:

var height: Int {
    return 5
}    

Try to print height's value, obviously works. So far so good

print(height) // prints 5

However if you try to set it to a new value then you'll get an error:

height = 8 // ERROR  

error: cannot assign to value: 'height' is a get-only property

---

Answer:

Based on Martin's answer, I first wrote:

set(newValue) {
    height = newValue 
}

Which put a ton of load on my memory and led me to this question. Please take a look. So then I was figuring out what to write, and I kind of understood that if you don't want to do anything special you shouldn't be using computed properties and instead you should just use normal stored properties.

So I wrote a similar code

protocol Human {

    var height: Float {get set}

}

struct Boy: Human {

    // inch
    var USheight : Float

    // cm
    var height: Float {
        get {
            return 2.54 * USheight
        }
        set(newValue) {
         USheight = newValue/2.54

        }
    }
}

// 5 ft person
var person = Boy(USheight: 60)
 // interestingly the initializer is 'only' based on stored properties because they
 // initialize computed properties. 


// equals to 152cm person
print(person.height) // 152.4

---

Pro tip: When should you should make your properties read-only?

Normally if you make a property to be read-only ie { get } it's because those properties are computed and you don't want the object to have control over it.

Example you have a JSON object. It has multiple big objects like:

JSONData
 - userInfo (name, address, age)
 - devices (iPads, iPhones, Mac books)
 - credentials (basic iCloud, pro iCloud, celebrity)

by making the role a read-only you're only allowing the server to tell the code base the role of the user.

protocol Credentials {
    var role: String { get }

    init(person: Person)
}

class Person {
    var userInfo: String
    var devices: [String]
    var creds: Credentials {
        Credentials(person: self)
    }

    init(userInfo: userInfo, devices: [String]) {
        self.userInfo = userInfo
        self.devices = devices
    }
}