kotlin-fun
所属分类：Kotlin编程
开发工具：Java
文件大小：74KB
下载次数：0
上传日期：2016-10-19 21:02:15
上 传 者：
sh-1993
说明： 玩Kotlin并实现有趣的东西
(Playing around with Kotlin and implementing interesting stuff)
文件列表:
build.gradle (817, 2016-10-20)
gradle (0, 2016-10-20)
gradle\wrapper (0, 2016-10-20)
gradle\wrapper\gradle-wrapper.jar (53636, 2016-10-20)
gradle\wrapper\gradle-wrapper.properties (230, 2016-10-20)
gradlew (4971, 2016-10-20)
gradlew.bat (2314, 2016-10-20)
settings.gradle (32, 2016-10-20)
src (0, 2016-10-20)
src\main (0, 2016-10-20)
src\main\java (0, 2016-10-20)
src\main\java\com (0, 2016-10-20)
src\main\java\com\github (0, 2016-10-20)
src\main\java\com\github\h0tk3y (0, 2016-10-20)
src\main\java\com\github\h0tk3y\kotlinFun (0, 2016-10-20)
src\main\java\com\github\h0tk3y\kotlinFun\util (0, 2016-10-20)
src\main\java\com\github\h0tk3y\kotlinFun\util\WeakIdentityHashMap.java (32591, 2016-10-20)
src\main\kotlin (0, 2016-10-20)
src\main\kotlin\com (0, 2016-10-20)
src\main\kotlin\com\github (0, 2016-10-20)
src\main\kotlin\com\github\h0tk3y (0, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun (0, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\ComparatorContext.kt (707, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\Events.kt (2139, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\FieldProperty.kt (4895, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\LexComparator.kt (1152, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\SelfReference.kt (835, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\SequenceChaining.kt (1163, 2016-10-20)
src\main\kotlin\com\github\h0tk3y\kotlinFun\VarWithObservableSetter.kt (1071, 2016-10-20)
src\test (0, 2016-10-20)
src\test\kotlin (0, 2016-10-20)
src\test\kotlin\com (0, 2016-10-20)
src\test\kotlin\com\github (0, 2016-10-20)
src\test\kotlin\com\github\h0tk3y (0, 2016-10-20)
src\test\kotlin\com\github\h0tk3y\kotlinFun (0, 2016-10-20)
src\test\kotlin\com\github\h0tk3y\kotlinFun\EventTest.kt (954, 2016-10-20)
src\test\kotlin\com\github\h0tk3y\kotlinFun\FieldPropertyTest.kt (2057, 2016-10-20)
... ...
# kotlin-fun
You know, writing code in Kotlin is a lot of `fun`.
Here you may find some useful stuff written while playing around. Contributions are welcome.
## Usage
You can use the project as a Gradle, Maven or SBT dependency:
[](https://jitpack.io/#h0tk3y/kotlin-fun)
## Self-reference
Kotlin has no ability to reference a variable which is not initialized inside its constructor.
But sometimes it is necessary, e.g. for callbacks.
Here is a workaround with the following usage:
val c: MyClass = selfReference { MyClass(someParams) { println(self.someField); } }
Here, `self` is a *magic* reference to a value which is not constructed yet.
## Sequence chaining
* `modifyPrefix` takes the original sequence and applies an operator to its prefix, leaving the
tail unchanged, if any;
* `chain` transforms the sequence by chaining the results of the operators, each called on what's left of the sequence
after the previous one;
* `lazyChain` is the same but concatenation is done lazily and no sequence objects are created until their items item are
requested;
* operator for concatenating a sequence with lambda that provides a sequence.
### Examples
val seq = (1..5).asSequence()
val prefixModified = seq.modifyPrefix { drop(1).take(2).map { -it } } // -2, -3, 4, 5
val chained = seq.chain(
{ sequenceOf(-1, 0) }
{ take(2).map { it + 100 } }
{ map { it * 100 } }
)
// -1, 0, 101, 102, 300, 400, 500
fun primes(): Sequence {
fun primesFilter(from: Sequence): Sequence = from.iterator().let {
val current = it.next()
sequenceOf(current) + { primesFilter(it.asSequence().filter { it % current != 0 }) }
}
return primesFilter((2..Int.MAX_VALUE).asSequence())
}
## Field property delegate
Provides property delegates which behave as if there was a backing field. Useful for extension properties.
Use `[Synchronized][Nullable]FieldProperty` for properties with different nullability and thread-safety.
Default initializer for nullable version produces `null`, for not-null -- throws `IllegalStateException`.
var MyClass.tag: String by FieldProperty { it.name }
fun main(args: Array) {
val c = MyClass("some name")
println(c.tag) // some name
c.tag = "some tag"
println(c.tag) // some tag
}
Can be used to create inner mapping distinct for instances of enclosing class:
val enclosingMyClassSharedTag = FieldProperty { it.name.reversed() }
class Enclosing {
var MyClass.innerTag: String by FieldProperty { it.name }
var MyClass.sharedTag: String by enclosingMyClassSharedTag
// ...
}
## Lexicographical comparator
Given a `Comparator`, creates a `Comparator>`, that compares iterables lexicographically:
val natural = naturalOrder()
val comparator = natural.lexicographically()
comparator.compare(listOf(1, 2, 3), listOf(1, 2, 3, 4)) // -1
comparator.compare(listOf(1, 2, 4), listOf(1, 2, 3, 4)) // 1
## Comparator context
Allows you to use comparison operators `<`, `>`, `<=`, `>=` when you have a comparator for the corresponding type.
val compareBySizes = compareBy> { it.size }
compareBySize.withOperators {
println(listOf(1) < listOf(1, 2)) // true
println(listOf(1, 2, 3) >= listOf(3, 2, 1)) // true
}
Cannot be used for `Comparator>` because of the operators being extension functions.
## Var with observable setter
Provides a property delegate with Swift-style `didSet` and `willSet` observers, and a type-safe builder for it, that allows you to add any one of `didSet` and `willSet` or both:
var x: Int by varWithObservableSetter(5).willSet { println("before") }.didSet { println("after") }
var y: String by varWithObservableSetter("abc").didSet { println("after") }
## Events
C#-like events with handlers subscription. Supports adding a fire-once handler. Handler functions can receive zero to three arguments.
val e = event0()
e.addHandler { println("triggered!") }
e.trigger() // triggered!
val tick = event2()
val f = { code, tag -> print("$code $tag " }
e.addHandler(f)
e.handleOnce { code, tag -> println(code + tag.length) }
e.trigger(1, "abc") // 1 abc 4
e.trigger(2, "def") // 2 def
e.removeHandler(f)
e.trigger(3, "xyz") //
To avoid exposing `trigger()` function to 3rd party code, use `.asHandlersCollector()`
private val e = event1()
val event: HandlersCollector<(String) -> Unit> get() = e.asHandlersCollector()
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