digitalmars.D.learn - Naming methods from strings using mixin
- Robert Rouse (16/16) Feb 21 2012 Using a mixin, is it possible to have it define a method based on
- Adam D. Ruppe (30/32) Feb 21 2012 Yeah, though you'll have to build a string of the method.
- Robert Rouse (2/35) Feb 21 2012
- Vladimir Panteleev (7/9) Feb 21 2012 A simpler way:
- Robert Rouse (14/24) Feb 21 2012 Hello again,
- Adam D. Ruppe (7/8) Feb 21 2012 Did you remember to new the class?
- Robert Rouse (6/15) Feb 21 2012 I did not.
- Robert Rouse (3/25) Feb 21 2012 Nevermind.. I had it as struct playing around and didn't change
Using a mixin, is it possible to have it define a method based on
a string passed into the mixin?
An example of what I'm hoping to do:
mixin template make_method(string name) {
void name() { // not sure how to make it become "void
bark()" here
writeln("hello");
}
}
class Animal {
mixin make_method!("bark");
}
Animal a;
a.bark();
Any help would be appreciated. I'm hoping D can do this since it
would make something I'm trying to do easier.
Feb 21 2012
On Tuesday, 21 February 2012 at 14:53:06 UTC, Robert Rouse wrote:Using a mixin, is it possible to have it define a method based on a string passed into the mixin?Yeah, though you'll have to build a string of the method. Something like this: string make_method_string(string name) { string code = "void "; // return type code ~= name; code ~= "() {"; // arglist code ~= q{ // body (q{ } is just another string literal but prettier for this imo writeln("hello"); }; code ~= "}"; return code; } mixin template make_method(string name) { mixin(make_method_string(name)); // string mixin runs the above function at compile time, and then pastes the resulting code in here to be compiled } // and now to use it struct Test { mixin make_method("bark"); } void main() { Test foo; foo.bark(); // works! } The string mixin and string builder helper function pattern can do pretty much anything you can think up, though it can get pretty ugly as it gets bigger just due to being strings.
Feb 21 2012
Robert Rouse <robert.e.rouse gmail.com> Awesome. Thanks! Adam D. Ruppe wrote:On Tuesday, 21 February 2012 at 14:53:06 UTC, Robert Rouse wrote:Using a mixin, is it possible to have it define a method based on a string passed into the mixin?Yeah, though you'll have to build a string of the method. Something like this: string make_method_string(string name) { string code = "void "; // return type code ~= name; code ~= "() {"; // arglist code ~= q{ // body (q{ } is just another string literal but prettier for this imo writeln("hello"); }; code ~= "}"; return code; } mixin template make_method(string name) { mixin(make_method_string(name)); // string mixin runs the above function at compile time, and then pastes the resulting code in here to be compiled } // and now to use it struct Test { mixin make_method("bark"); } void main() { Test foo; foo.bark(); // works! } The string mixin and string builder helper function pattern can do pretty much anything you can think up, though it can get pretty ugly as it gets bigger just due to being strings.
Feb 21 2012
On Tuesday, 21 February 2012 at 14:53:06 UTC, Robert Rouse wrote:Using a mixin, is it possible to have it define a method based on a string passed into the mixin?A simpler way: mixin template MakeMethod(string name) { void _MakeMethod_method() { /* ... */ } mixin("alias _MakeMethod_method " ~ name ~ ";"); }
Feb 21 2012
Hello again,
Both methods work as long as the object I call the mixin within
is a struct
struct Test {
mixin MakeMethod!("bark");
}
If I switch struct to class
class Test {
mixin MakeMethod!("bark");
}
it segfaults.
What am I missing?
On Tuesday, 21 February 2012 at 15:29:49 UTC, Vladimir Panteleev
wrote:
On Tuesday, 21 February 2012 at 14:53:06 UTC, Robert Rouse
wrote:
Using a mixin, is it possible to have it define a method based
on a string passed into the mixin?
A simpler way:
mixin template MakeMethod(string name)
{
void _MakeMethod_method() { /* ... */ }
mixin("alias _MakeMethod_method " ~ name ~ ";");
}
Feb 21 2012
On Tuesday, 21 February 2012 at 18:07:34 UTC, Robert Rouse wrote:What am I missing?Did you remember to new the class? class MyClass {} MyClass a; // a is null right now a = new MyClass(); // gotta remember this That's different than structs (or classes in C++) which work without being new'd.
Feb 21 2012
I did not. Trying to new it gives me a compile error since "MyClass a" is not a pointer. If I define another method without mixin and call it before the "mixin" one, it works. On Tuesday, 21 February 2012 at 18:13:30 UTC, Adam D. Ruppe wrote:On Tuesday, 21 February 2012 at 18:07:34 UTC, Robert Rouse wrote:What am I missing?Did you remember to new the class? class MyClass {} MyClass a; // a is null right now a = new MyClass(); // gotta remember this That's different than structs (or classes in C++) which work without being new'd.
Feb 21 2012
Nevermind.. I had it as struct playing around and didn't change it back On Tuesday, 21 February 2012 at 18:37:02 UTC, Robert Rouse wrote:I did not. Trying to new it gives me a compile error since "MyClass a" is not a pointer. If I define another method without mixin and call it before the "mixin" one, it works. On Tuesday, 21 February 2012 at 18:13:30 UTC, Adam D. Ruppe wrote:On Tuesday, 21 February 2012 at 18:07:34 UTC, Robert Rouse wrote:What am I missing?Did you remember to new the class? class MyClass {} MyClass a; // a is null right now a = new MyClass(); // gotta remember this That's different than structs (or classes in C++) which work without being new'd.
Feb 21 2012