[英]How do I get the class (scope) from which a closure is called in Groovy?
class Box {
Closure click
Box () {
click = {}
}
void onClick() {
click()
}
}
class TextBox extends Box {
List<String> content
TextBox (String[] a) {
super()
content = a
}
}
class Main {
public static void main(String[] args) {
Main m = new Main()
}
Main() {
String[] a = ["Hello world!"]
Box b = new TextBox(a)
b.click = {content.add("You clicked this box!")}
b.onClick() //throws Exception
}
}
(The above is, obviously, a simplification; in reality, the classes are a bit more involved, and calling of onClick() is due to a click on a JFrame) (显然,上面是一个简化;实际上,类更多涉及,并且onClick()的调用是由于点击JFrame)
Now, when I try to run that (ie run Main.main()), I get an exception: Exception in thread "AWT-EventQueue-0" groovy.lang.MissingPropertyException: No such property: content for class: Main 现在,当我尝试运行它(即运行Main.main())时,我得到一个异常:线程“AWT-EventQueue-0”中的异常groovy.lang.MissingPropertyException:没有这样的属性:类的内容:Main
Clearly, it is, for some reason, searching for the List in Main, not in TextBox or Box, from where it is called. 显然,出于某种原因,它是在Main中搜索List,而不是在TextBox或Box中搜索它的位置。 I also tried using this, owner and delegate, but they all point to Main as well. 我也试过使用这个,所有者和代表,但他们都指向Main。 I managed to have it work by giving this as an argument: 我设法让它作为一个参数:
...
void onClick() {
click(this)
}
...
b.click = {it.content.add("You clicked this box!")}
It seems, however, weird to actually need to pass "this" to a closure just for it to be able to know where it was called from. 然而,实际上需要将“this”传递给闭包只是因为它能够知道从哪里调用它,这似乎很奇怪。 Isn't there a more elegant solution? 难道没有更优雅的解决方案吗? Also, even if it is indeed impossible to get into the TextBox-scope, is it somehow possible to get into the Box-scope? 而且,即使确实无法进入TextBox范围,是否有可能进入Box-scope?
Main() {
String[] a = ["Hello world!"]
Box b = new TextBox(a)
println "1:- $b.click.delegate" //Will print TextBox
b.click = {
println "2:- $b.click.delegate" //Will print Main
//Since the closure is now defined inside Main(),
//Main becomes the delegate. Reset the delegate to TextBox.
b.click.delegate = b
println "3:- $b.click.delegate" //Will print TextBox
content.add("You clicked this box!")
}
println "4:- $b.click.delegate" //Will print Main
b.onClick()
println b.content //Will print [Hello world!, You clicked this box!]
}
//Output:
1:- TextBox@c166770
4:- Main@6dbdc863
2:- Main@6dbdc863
3:- TextBox@c166770
[Hello world!, You clicked this box!]
Points to note: 注意事项:
TextBox
but Sequence 4 prints Main
. 序列1打印TextBox
但序列4打印Main
。 Note that the delegate
has changed (after defining closure b.click
) from TextBox
to Main
by now. 请注意, delegate
已经从TextBox
更改(在定义闭包b.click
)到Main
。 To make things easier, instead of changing things in Main
, you can just modify onClick()
as 为了onClick()
,您可以将onClick()
修改为,而不是在Main
中更改内容
void onClick() {
click.delegate = this
click()
}
Refer this script for details. 有关详细信息,请参阅此脚
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