Is there a way of delaying evaluation of string te...

# announcements

[Paul N]

Is there a way of delaying evaluation of string templates ?

So if I have this at a class level

val baseURL = "http://$domainName/endpoint"

and then a function like this

fun someMore(domainName : String, somethingElse : String) {
val x = "$baseURL$somethingElse
}

then x should equal http://mydomainname/endpoint/mysomethingElse if I pass in mydomainname and mysomethingelse to the function ?

[LeoColman]

Maybe you can use a lazy delegate?

[LeoColman]

val baseUrl by lazy { "http://$domainName/endpoint" }

[LeoColman]

it will only be evaluated once it's accessed

[LeoColman]

But idk if this is what you mean

[LeoColman]

You can also use a format for that, instead of trying to use the template "foo".format(..)

[Paul N]

Yes that's exactly what I mean - great, thanks !

[streetsofboston]

To defer the execution of a val, provide a getter:
val baseURL get() = "http://$domainName/endpoint"
Only when called/used the string will be evaluated.

[pniederw]

I don't think these solutions will work as $domainName will be resolved in the original class scope rather than in function scope. One solution I can think of is to turn baseURL into a lambda that accepts domainName as parameter.

[Paul N]

The get() doesn't work as you get a compile error as the domain name doesn't exist

[Paul N]

The lambda solution works - thanks @pniederw

[Mike]

This ‘feels’ risky. baseURL will use the domainName available at the moment in time when it’s executed. If someMore is called more than once, with a different domainName, you won’t get the result you want as baseURL will always return the first value.

If someMore IS only called once, then there’s likely a cleaner way to set the domainName in baseURL.

[Stefan Beyer]

why not

fun baseURL(domainName: String) = 
    "http://$domainName/endpoint"
fun someMore(domainName: String, somethingElse: String) {
    val x = "${baseURL(domainName)}$somethingElse"
}