Hi,
I can create stored properties for eg lastName, firstName.
var lastName: String
var firstName: String
...
But what in case if I want eg:
- if I want to have the possibility to change the lastName and/or firstName during the lifecycle of the object.
- test if the passed value for lastName and/or firstName is empty or not
What is the way to do this in Swift?
Thanks.
Guy
class MyClass {
var lastName: String
var firstName: String
init(lastName: String, firstName: String) {
self.lastName = lastName
self.firstName = firstName
}
}
let object = MyClass(lastName: "Taro", firstName: "Yamada")
//- if I want to have the possibility to change the lastName and/or firstName during the lifecycle of the object.
object.lastName = "Hanako"
object.firstName = "Sato"
//- test if the passed value for lastName and/or firstName is empty or not
if object.lastName.isEmpty || object.firstName.isEmpty {
print("empty")
}I may be mistaking the intention of your question, if so, please be more specific about what you really want to do.
I think he's complaining about the fact (at least I think it's a fact - maybe you could confirm) that if you want to override get and set then it has to be a computed property, not a stored property. And I suppose you would need a separate private stored property so the computed property's getter and setter would have something to do.
class TestProperties {
private var storedProperty: String = ""
var someProperty: String {
get {
// possibly modify the return value
return storedProperty + " modified"
}
set {
// possibly modify the value being stored
storedProperty = "foo " + newValue
}
}
}
let test = TestProperties()
test.someProperty = "bar"
print("\(test.someProperty)") // "foo bar modified"I suppose there is willSet / didSet on a stored property but nothing on the getter side.
Thanks. To clarify a little bit what I'm looking for in Swift, see the code below (C#). In Java this would be almost the same. This code let's you test 1) if the passed in values are correct and 2) give the possibility to change a value when needed.
Remark: this is only an example to show what I would like to achieve, normally eg you wouldn't change the id of a person object.
Thanks.
public class Person
{
private int id;
private string lastName;
public Person(int id, string lastName) -> corresponds with init(...)
{
Id = id;
LastName = lastName;
}
public int Id
{
get
{
return this.id;
}
set
{
if (value < 0 || value > 1000)
{
// throw error
}
else
{
this.id = value;
}
}
}
public string LastName
{
get
{
return this.lastName;
}
set
{
if (value == null)
{
// throw error
}
else
{
this.lastName = value;
}
}
}
}
Your code converted to Swift:
public class Person {
private var _id: Int = 0
private var _lastName: String = ""
public init(id: Int, lastName: String) {
self.id = id
self.lastName = lastName
}
public var id: Int {
get {
return self._id;
}
set {
if newValue < 0 || newValue > 1000 {
// Swift setter cannot throw error.
fatalError("invalid value for id")
} else {
self._id = newValue
}
}
}
public var lastName: String {
get {
return self._lastName
}
set {
// In Swift, non-optional String can never get nil.
if newValue.isEmpty {
fatalError("invalid value for lastName")
} else {
self._lastName = newValue
}
}
}
}I believe this code fulfills your demand:
This code let's you test 1) if the passed in values are correct and 2) give the possibility to change a value when needed.
You may need to reconstruct your error handling strategy in Swift, but defining properties does not seem to be different.
Hi,
Thanks.
I suppose another option to implement the behavior could be:
private var lastName: String = ""
public func getLastName() -> String {
return self.lastName;
}
public func setLastName(description: String) {
if description.isEmpty {
fatalError("invalid value for lastName")
} else {
self.lastName = lastName
}
}
If this is so what is the 'recommended' way to implement the required behavior?
Thanks.
Guy
I believe it's just `another` way of doing the same thing. Generally, it is hard to find getters with their names begin with `get` in Apple's frameworks, so you can take it as `not recommended`.
But Swift is a new language and it seems not to be having so many established `recommended`.
Since Swift 2 introduced new error handling, using `throws` is being a preferred way for many programmers.
enum PersonError: ErrorType {
case InvalidLastName
}
private(set) var lastName: String = ""
func setLastName(lastName: String) throws {
if lastName.isEmpty {
throw PersonError.InvalidLastName
} else {
self.lastName = lastName
}
}Find your own `recommended` way and introduce it to other developers.