how to deal with stored properties's set and get in swift - objective-c

Question

this is a way we deal with property in OC
- (void)setText:(NSString *)text
{
if ([text isEqualToString:#"ss"]) {
_text = #"xx";
return
}
_text = text;
}
- (NSString *)text
{
return _text;
}
this is a wrong way in swift, we can't call self.xx in set.
var text : NSString {
get {
return self.text
}
set {
if newValue.isEqualToString("ss") {
self.text = "xx"
} else {
self.text = newValue
}
}
}
My question is how to transfer the OC code to Swift code.

Answer 1

You're confusing stored properties with computed properties.
Only computed properties have a getter and an optional setter; stored properties don't have either. Also, the setter in a computed property isn't there to set the value of the computed property (it can't, as the property is, well, computed and does not have an independent existence); rather, it's used to set the values of other properties, whose values are used to compute the computed property when it's next accessed. See this post for an example of that.
Now, stored properties can have property observers. In your specific example, it would look like this:
var text : NSString! {
didSet {
if text.isEqualToString("ss" as NSString) {
text = "xx" as NSString
}
}
}
You can also have a willSet block. Note that in Swift 1.2 NSString and String are no longer automatically bridged so you need to cast them onto each other when necessary.

Answer 2

While I don't know much about using a getter and setter on a stored property, in your case you can just use a property observer didSet.
var text: String! {
didSet {
if text == "ss" {
text = "xx"
}
}
}

Answer 3

You can try this way!
var text: NSString = ""
var newText : NSString {
get {
return text
}
set {
if newValue.isEqualToString("ss") {
text = "xx"
} else {
text = newValue
}
}
}