• simendsjo (47/47) Jan 08 2012 C# has Object Initializers:

simendsjo <simendsjo gmail.com> writes:

http://msdn.microsoft.com/en-us/library/bb384062.aspx
Java has Double Brace Initializers: 
http://www.c2.com/cgi/wiki?DoubleBraceInitialization

D has with: http://dlang.org/statement.html#WithStatement

The nice thing about object initializers is that you can initialize 
properties not supported by ctor in-place:
someFunction(new C { property = value });
or
new C {
   d = new D { /*something*/ }
}

Are there a good D idom to do something like this? I'm pretty sure 

though :)

This is a little test using mixin (which obviously isn't of any real use)

T init(T, string Q, A...)(A params) {
     auto c = new T(params);
     with(c) {
         mixin(Q);
     }
     return c;
}

class C {
     int _i;
      property void prop(int i) { _i = i; }

     string _a;
     int _b;
     this(string a, int b) {
         _a = a;
         _b = b;
     }
}

void main() {
     auto c = init!(C, q{ prop = 10; })("a", 2);
     assert(c._i == 10);
     assert(c._a == "a");
     assert(c._b == 2);
}

Or with a delegate instead:
T init(T, A...)(void delegate(T) dg, A params) {
     auto c = new T(params);
     dg(c);
     return c;
}

auto c = init!(C)((C o) { o.prop = 10; }, "a", 2);

Extremely ugly and hard to read :)