是否可以在kotlin中使用unaryPlus调用函数? [英] Is it possible to invoke a function with a unaryPlus in kotlin?
问题描述
这是我昨天问的另一个问题的后续问题.
This is a followup question on another question I asked yesterday.
由于提供了很好的答案，请致谢:佩洛乔.
Credit to: Pelocho for giving nice answer.
我使用本教程进行类型安全的graphQL查询建造者:
I used this Tutorial to do a type safe graphQL query builder:
我现在想做的就是简化我所做的事情 而且我知道kotlin必须具有一些不错的功能才能做到这一点.
What I want to do now is to simplify what I made And I know that kotlin must have some nice features to do that.
现在，当我想向查询中添加实体时，我必须调用函数:
Right now I have to invoke functions when I want to add an entity to my query:
fun main() {
events{
title() // I don't like to do () when it is an edge case
}
}
我想知道是否可以做一些不同的，更简单的事情，例如:
I am wondering if it is posible to do something different, and more simple, like:
fun main() {
events{
title // this is much nicer
}
}
但是如果不可能的话，可以通过操作符重载来减少字符数，例如. unaryPlus
But if it is not possible then it is ok just to reduce the amount of characters with an operator overloading like eg. unaryPlus
fun main() {
events{
+title // this is also nicer
}
}
我现在拥有的代码有一个名为Query的类，在其中放置了方法:
My code that I have now has a class called Query where I put the method:
operator fun Query.unaryPlus() {
visitEntity(this,{})
}
但是它似乎对我不起作用.
But it does not seem to work for me.
我所有的代码都在这里.
All my code is here.
interface Element {
fun render(builder: StringBuilder, indent: String)
}
@DslMarker //Domain Specific Language
annotation class GraphQLMarker
@GraphQLMarker
abstract class Query(val name: String) : Element {
val children = arrayListOf<Element>()
protected fun <T : Element> visitEntity(entity: T, visit: T.() -> Unit = {}): T {
entity.visit()
children.add(entity)
return entity
}
override fun render(builder: StringBuilder, indent: String) {
builder.append("$indent$name")
if (children.isNotEmpty()) {
builder.append("{\n")
for (c in children) {
c.render(builder, "$indent ")
}
builder.append("$indent}")
}
builder.append("\n")
}
operator fun Query.unaryPlus() {
visitEntity(this,{})
}
override fun toString(): String {
val builder = StringBuilder()
render(builder, "")
return builder.toString()
}
}
然后我创建了与我的案例相关的类
Then I created the classes relevant to my case
class Filter private constructor(val filters: MutableMap<FilterType, Any>) {
class Builder {
private val filters = mutableMapOf<FilterType, Any>()
fun filters(key: FilterType, value: Any) = apply {
this.filters[key] = value
}
fun build(): Filter {
return Filter(filters)
}
}
}
class EVENTS(private val filter: Filter) : Query("events") {
override fun render(builder: StringBuilder, indent: String) {
builder.append("{$name")
if (filter.filters.isNotEmpty()) {
builder.append("(" + filter.filters.map {
if (it.value is Int || it.value is Long) {
it.key.str + ":" + it.value + ","
} else {
it.key.str + ":\"" + it.value + "\","
}
}.joinToString(" ").dropLast(1) + ")")
}
if (children.isNotEmpty()) {
builder.append("{\n")
for (c in children) {
c.render(builder, "$indent ")
}
builder.append("$indent}")
}
builder.append("\n}")
}
fun title() = visitEntity(TITLE())
fun genre() = visitEntity(GENRE())
fun image() = visitEntity(IMAGE())
fun link() = visitEntity(LINK())
fun other() = visitEntity(OTHER())
fun price() = visitEntity(PRICE())
fun text() = visitEntity(TEXT())
fun tickets() = visitEntity(TICKETS())
fun time() = visitEntity(TIME())
fun location(visit: LOCATION.() -> Unit) = visitEntity(LOCATION(), visit)
}
class TITLE : Query("title")
class GENRE : Query("genre")
class IMAGE : Query("image")
class LINK : Query("link")
class OTHER : Query("other")
class PRICE : Query("price")
class TEXT : Query("text")
class TICKETS : Query("tickets")
class TIME : Query("time")
class LOCATION : Query("location") {
fun area() = visitEntity(AREA())
fun place() = visitEntity(PLACE())
fun address(visit: ADDRESS.() -> Unit) = visitEntity(ADDRESS(), visit)
fun coordinates(visit: COORDINATES.() -> Unit) = visitEntity(COORDINATES(), visit)
}
class AREA : Query("area")
class PLACE : Query("place")
class ADDRESS : Query("address") {
fun city() = visitEntity(CITY())
fun street() = visitEntity(STREET())
fun no() = visitEntity(NO())
fun state() = visitEntity(STATE())
fun zip() = visitEntity(ZIP())
}
class CITY : Query("city")
class STREET : Query("street")
class NO : Query("no")
class STATE : Query("state")
class ZIP : Query("zip")
class COORDINATES : Query("coordinates") {
fun longitude() = visitEntity(LONGITUDE())
fun latitude() = visitEntity(LATITUDE())
}
class LONGITUDE : Query("longitude")
class LATITUDE : Query("latitude")
enum class FilterType(val str: String) {
PLACE("place"),
PRICELT("priceLT"),
PRICEGT("priceGT"),
TIMELT("timestampLT"),
TIMEGT("timestampGT"),
AREA("area"),
TITLE("title"),
GENRE("genre")
}
其中一些类别是 edgecases ，因此不会将它们嵌套得更深.所以我在想是否可以简化一下.而且，当我从main()函数调用它们时，如果可以使用unaryPlus来调用它们，那么当它们没有嵌套的任何等待时，我就不必在非常单一的边缘情况下编写{}
Some of the classes are edgecases and will not nest themself further down. So I was thinking if it is possible to simplify that a bit. And if I can use a unaryPlus to invoke them when I call them from the main() function, so I dont have to write {} after very single edgecase, when they dont have nesting anywaits
fun main(){
events(filter) {
title()
genre()
image()
link()
tickets()
other()
price()
text()
time()
location {
area()
place()
address {
city()
street()
no()
state()
zip()
}
coordinates {
longitude()
latitude()
}
}
}
}
先谢谢您.祝你有美好的一天！
Thank you in advance. Have a nice day!
推荐答案
是的，您可以根据需要使用unaryPlus
Yes, you can use unaryPlus for whatever you want
查看操作员重载文档
这里有一个有效的示例:
Here you have a working example:
fun main() {
val events = events {
+title
+genre
}
println(events.render())
}
interface Element {
fun render() : String
}
@DslMarker //Domain Specific Language
annotation class GraphQLMarker
@GraphQLMarker
fun events(init: EventBody.() -> Unit): Element {
val events = EventBody()
events.init()
return events
}
class EventBody: Element {
override fun render() =
"events:${elements.joinToString { it.render() }}"
private val elements = mutableListOf<Element>()
operator fun Element.unaryPlus() = elements.add(this)
}
@GraphQLMarker
object title: Element {
override fun render() = "title"
}
@GraphQLMarker
object genre: Element {
override fun render() = "genre"
}
输出
events:title, genre
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