Sitting here at FOSDEM today I was showing Remi my new addition to
InvokeBinder: named arguments.
Background: InvokeBinder is my little Java DSL/fluent API for building
method handle chains. Short example:
MethodHandle mh = Binder
.from(String.class, String.class, String.class) // String w(String, String)
.drop(1, String.class) // String x(String)
.insert(0, 'hello') // String y(String, String)
.cast(String.class, CharSequence.class, Object.class) // String
z(CharSequence, Object)
.invoke(someTargetHandle);
The new stuff I added is a Signature class for managing a MethodType
along with an array of argument names, and SmartBinder to take
advantage of that. How is this useful? The above example might be
reworked as follows:
Signature sig = Signature
.returning(String.class)
.appendArg("arg1", String.class)
.appendArg("arg2", String.class);
MethodHandle mh = SmartBinder
.from(sig)
.drop("arg2") // String x(String)
.prepend("argX", 'hello') // String y(String, String)
.cast(String.class, CharSequence.class, Object.class) // String
z(CharSequence, Object)
.invoke(someTargetHandle);
So we can always use the argument names rather than error-prone
indices. This is especially useful for permutes, which I consistently
get completely wrong:
MethodHandle incoming = handle with signature below;
Signature sig = Signature
.returning(String.class)
.appendArg("arg1", String.class)
.appendArg("arg2", String.class)
.appendArg("arg3", String.class);
// permute without indices!
MethodHandle permuted = sig.permuteWith(incoming, "arg1", "arg3");
This is not in an InvokeBinder release yet because I want to add all
Binder operations to SmartBinder, but I'm looking for feedback and
other use cases for named arguments in the signature. Thanks!
- Charlie
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