Using contains on a string array with ignoreCase

Question

I have a string array and I want to check if it contains some string while ignoring the case, so I do

businessCategories.contains(currentCategory, ignoreCase = true)

but it displays the error:

Cannot find a parameter with this name: ignoreCase

Why doesn't my list recognise the param ignoreCase? I read about the function in a few places: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/contains.html and https://bladecoder.medium.com/the-kotlin-standard-function-will-not-just-improve-readability-in-this-case-but-performance-as-well-5515822ce216, so why is ignoreCase not available?

businessCategories isn't a CharSequence, it's an array? The documentation you've linked is for a CharSequence. The function you're calling is this: kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/… — Henry Twist
– Henry Twist, Commented May 15, 2021 at 15:49
@HenryTwist just realized that lol. So list doesn't have ignoreCase method? Means I need to convert businessCategories to CharSequence first? Or is there a better way? — imin
– imin, Commented May 15, 2021 at 15:53
No it doesn't. It checks whether the list contains a specific element. Are you looking to check whether the list contains a specific string ignoring case? If so then you want something like this: elements.any { it.equals("Something", ignoreCase = true) } — Henry Twist
– Henry Twist, Commented May 15, 2021 at 15:55
You can't just use any Kotlin function on an array and expect it to check the whole array, that would be very ambiguous. Also you can't 'convert' a list to a CharSequence without defining what that means: concatenating it? Adding commas in between? Etc. — Henry Twist
– Henry Twist, Commented May 15, 2021 at 15:57
elements.any { it.equals("Something", ignoreCase = true) } is what I actually need. Can you post it as the answer so that I can accept it, and maybe add a little more explanation to it that may help new Kotlin learners understand more? — imin
– imin, Commented May 15, 2021 at 16:09

Henry Twist · Accepted Answer · 2021-05-15 16:18:16Z

5

You seem to be mixing up your types here. The documentation you linked refers to the contains method on a CharSequence, which checks whether a string is a 'superstring' of another. What you're probably after is to check whether any element of your array is equal to a specific string, whilst ignoring case.

Unfortunately I don't think there is a function in the standard library to achieve this, but you can use Array<T>.any along with String?.equals to check each element, something like this:

val myString = "..."
stringArray.any { it.equals(myString, ignoreCase = true) }

You could even define a nice extension function:

fun Array<String>.contains(s: String, ignoreCase: Boolean = false): Boolean {
    
    return any { it.equals(s, ignoreCase) }
}

answered May 15, 2021 at 16:18

Henry Twist

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gscaparrotti · Accepted Answer · 2023-07-06 14:59:57Z

0

There is no such feature in Kotlin itself, but in can be easily added using an extension function:

infix fun <T : CharSequence> T.inIgnoreCase(iterable: Iterable<T>): Boolean {
    return iterable.any { it.contentEquals(this, ignoreCase = true) }
}

It can be used this way:

val list = listOf("aaa", "bbb")
val string = "AAA"
string inIgnoreCase list // true

answered Jul 6, 2023 at 14:59

gscaparrotti

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