我认为这有一个简单的答案,但我的网络搜索找不到它。
如果我有以下(ideone):
def f() {}
class C
{
public h() { f() }
}
x = (new C()).h();
这失败并出现以下错误:
No signature of method: c.f() is applicable for argument types: () values: []
如何f()
从方法内部调用C
?
You need a reference to the "outer" class (which isn't really an outer class).
Assuming you are writing your code in a Script.groovy
file, it generates two classes: C.class
and Script.class
. There is no way to the C
call the f()
method, since it has no idea where it is defined.
You have some options:
1) @MichaelEaster's idea, giving a metaclass defition from the current scope (i.e. Script
)
2) Create/pass a Script
object inside C
:
def f() { "f" }
class C
{
public h(s = new Script()) { s.f() }
}
assert "f" == new C().h()
3) Make C
an inner class (which also needs an instance of Script
:
class Script {
def f() { "f" }
class C
{
public h() { f() }
}
static main(args) {
assert "f" == new C(new Script()).h()
}
}
4) Static inner class plus static f()
:
class Script {
static def f() { "f" }
static class C
{
public h() { f() }
}
static main(args) {
assert "f" == new C().h()
}
}
另一种不使用的方法metaClass
是定义h()
为闭包并使用:
def f() {}
class C {
def h = { f() }
}
x = (new C()).h
x.delegate = this
x()
这是使用元编程的一种方法:
def f() { println "Hello" }
class C
{
public h() { f() }
}
C.metaClass.f = { f() }
x = (new C()).h();