How can I escape a function name so that it can span multiple lines? For example
#Test
fun `This is a really long description of what should happen to this function when the IDs do not match up.`() {
// test
}
What I would want is something like
#Test
fun `This is a really long description of what should happen to this \
function when the IDs do not match up.`() { // test }
Is this possible?
It is not possible, function names convention allows spaces in test methods but not multiple lines : https://kotlinlang.org/docs/coding-conventions.html#names-for-test-methods
In tests (and only in tests), you can use method names with spaces enclosed in backticks.
A method with multiple lines in its name would not be callable even through reflection. (see https://stackoverflow.com/a/45750788/7346454)
Related
I want to create a Live Template for createSelector:
export const someSelector = createSelector(getThis, getThat, getSomethingElse, (this, that, somethingElse) =>
$END$
)
I can get it to work pretty well with a single argument (e.g., only getThis which then results in (this) in the arrow function args).
// template text
createSelector($someSelector$, ($variable$) => $END$)
// variables
// expression for "variable":
decapitalize(regularExpression(someSelector, "get", ""))
This works correctly with a single argument as mentioned above, and almost works correctly with multiple arguments, except for the capitalization:
createSelector(getThis, getThat, getSomethingElse, (this, That, SomethingElse) => /* $end$ */)
I tried wrapping that whole thing in camelCase but then of course the commas and spaces are gone.
The issue is clearly that I'm processing the whole string at once so the whole string is run through whatever string formatting function. There doesn't appear to be any way to treat individual instances of "get" separately.
I tried capture groups which I really thought would work:
decapitalize(regularExpression(someSelector, "get(\w+)", "$1"))
But that doesn't replace anything, it just copies the whole thing:
createSelector(getThis, getThat, (getThis, getThat) => )
Is there any way to accomplish this?
UPDATE:
I even learned Groovy script and wrote the following, which works in a groovy playground, but gets in WebStorm gets the same result as my final example above!
groovyScript("return _1.replaceAll(/get(\w+)/) { it[1].uncapitalize() };", someSelector)
This could be done with RegEx .. but Java does not seem to support \l replacement modifier (to be used as \l$1 instead of $1 in your initial regularExpression() code).
Live example (works in PCRE2, e.g. in PHP): https://regex101.com/r/6faVqC/1
Docs on replacement modifiers: https://www.regular-expressions.info/refreplacecase.html
In any case: this whole thing is handled by Java and you are passing RegEx pattern or GrovyScript code inside double quotes. Therefore any \ symbols would need to be escaped.
You need to replace get(\w+) by get(\\w+).
The following seems to work just fine for me here (where someSelector is the Live Template variable):
groovyScript("return _1.replaceAll(/get(\\w+)/) { it[1].uncapitalize() };", someSelector)
I'm recently trying to get into kotlin (coming from java) and did some beginner coding challenges.
The task is to write a function that capitalizes the first letter of every word in a string
I could solve the task in my own way, but I still don't understand this sample solution:
fun capitalizeSentence(str: String) {
println(str.split(" ").joinToString(" ") { it.capitalize() })
}
Can someone explain to me, why this lambda expressions manages to capitalize the first letter of every word, even when using the joinToString method right after the split method?
joinToString() accepts an optional transform function which it applies to each item before joining. It might be confusing to you, because this code performs operations in a different order than the code flow itself. This code is effectively an equivalent of this one:
str.split(" ")
.map { it.capitalize() }
.joinToString(" ")
I came across this line of code in Kotlin:
private val creators: ArrayMap<Class<*>,() ->ViewModel> = ArrayMap()
What does the comma mean? Is this a bug? According to this post, commas are not allowed:
Define multiple variables at once in Kotlin (e.g Java : String x,y,z;)
The comma separates the generic parameters of ArrayMap. The first parameter is Class<*>, while the second parameter is () -> ViewModel
Using kotlin I can repeat an action in at least two ways:
val times = 5
// First option
for (i in 0 until times) {
print("Action $i")
}
// Second option
repeat(times) {
print("Action $it")
}
I'd like to know the purpose of repeat.
Should the traditional for loop be replaced with repeat function if possible?
Or are there special cases for this function?
Are there any advantages in repeat function?
EDIT
I've made some research about this question. As long as kotlin is open source project, I could download the sources and check git history.
I found that
1) repeat function is a replace for times function extension.
public inline fun Int.times(body : () -> Unit)
2) KT-7074. times function has become deprecated. But why?
It's just a matter of convenience (shortens the code). There are even more ways for example using an IntRange and forEach
(0..4).forEach {
println(it)
}
0 1 2 3 4
They all serve the same purpose, so the choice is yours.
You don't need to worry about performance either, since repeat and forEach are inline functions, which means the lambda code is copied over to the call site at compile time.
Next lines are all just my opinion:
there are no special cases when you should or shouldn't use repeat
function.
it has more concise syntax.
In places where you don't need to manipulate the loop counter or need to repeat only some simple action I would use that function.
It's all up to you to decide when and how to use it.
From Standard.kt:
/**
* Executes the given function [action] specified number of [times].
*
* A zero-based index of current iteration is passed as a parameter to [action].
*
* #sample samples.misc.ControlFlow.repeat
*/
#kotlin.internal.InlineOnly
public inline fun repeat(times: Int, action: (Int) -> Unit) {
contract { callsInPlace(action) }
for (index in 0 until times) {
action(index)
}
}
As you can see repeat(times) is actually for (index in 0 until times).
There is also a zero-based loop counter and it is: it.
Should the traditional for loop be replaced with repeat function if
possible?
I can't find any reason for that
Or are there special cases for this function?
None I can think of.
Are there any advantages in repeat function?
None I can think of, or maybe(?) just 1:
for educational purposes, I suppose it's easier to teach
that repeat(n) { } performs n iterations of the block of statements inside the curly brackets.
How do I replace multiple characters in a String?
Like Java's replaceAll(regex:replacement:) function.
str.replaceAll("[$,.]", "") //java code
This answer is very close but I want to change more than one character at the same time.
[$,.] is regex, which is the expected input for Java's replaceAll() method. Kotlin, however, has a class called Regex, and string.replace() is overloaded to take either a String or a Regex argument.
So you have to call .toRegex() explicitly, otherwise it thinks you want to replace the String literal [$,.]. It's also worth mentioning that $ in Kotlin is used with String templates, meaning in regular strings you have to escape it using a backslash. Kotlin supports raw Strings (marked by three " instead of one) which don't need to have these escaped, meaning you can do this:
str = str.replace("""[$,.]""".toRegex(), "")
In general, you need a Regex object. Aside using toRegex() (which may or may not be syntactical sugar), you can also create a Regex object by using the constructor for the class:
str = str.replace(Regex("""[$,.]"""), "")
Both these signal that your string is regex, and makes sure the right replace() is used.
If you're happy to work with regular expressions, then refer to the accepted answer here. If you're curious as to how you can achieve this without regular expressions, continue reading.
You can use the String.filterNot(predicate:) and Set.contains(element:) functions to define a String.removeAll extension function as follows:
/**
* #param charactersToRemove The characters to remove from the receiving String.
* #return A copy of the receiving String with the characters in `charactersToRemove` removed.
*/
fun String.removeAll(charactersToRemove: Set<Char>): String {
return filterNot { charactersToRemove.contains(it) }
}
You would call on this function as follows: myString.removeAll(setOf('$', '.'))