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Class `std.typecons.AutoImplement`

AutoImplement automatically implements (by default) all abstract member functions in the class or interface Base in specified way.

Inherits from

Object (base class)

Methods

Name	Description
`factory`	Create instance of class specified by the fully qualified name `classname`. The class must either have no constructors or have a default constructor.
`opCmp`	Compare with another `Object` obj.
`opEquals`	Returns !=0 if this `object` does have the same contents as obj.
`toHash`	Compute hash function for `Object`.
`toString`	Convert `Object` to a human readable string.

Parameters

Name Description

how

Name	Description
how	template which specifies how functions will be implemented/overridden. Two arguments are passed to `how`: the type `Base` and an alias to an implemented function. Then `how` must return an implemented function body as a string. The generated function body can use these keywords: `a0`, `a1`, …: arguments passed to the function; `args`: a `tuple` of the arguments; `self`: an alias to the function itself; `parent`: an alias to the overridden function (if any). You may want to use templated property functions (instead of Implicit Template Properties) to generate complex functions: -------------------- // Prints log messages for each call to overridden functions. string generateLogger(C, alias fun)() @property { import `std.traits`; enum qname = C.stringof ~ "." ~ _traits(identifier, fun); string stmt; stmt ~= q{ struct Importer { import `std.stdio`; } }; stmt ~= `Importer.writeln("Log:` ~ qname ~ `(", args, ")");`; static if (!_traits(isAbstractFunction, fun)) { static if (is(ReturnType!fun == void)) stmt ~= q{ parent(args); }; else stmt ~= q{ auto r = parent(args); Importer.writeln("--> ", r); return r; }; } return stmt; } --------------------
what	template which determines what functions should be implemented/overridden. An argument is passed to `what`: an alias to a non-final member function in `Base`. Then `what` must return a boolean value. Return `true` to indicate that the passed function should be implemented/overridden. -------------------- // Sees if fun returns something. enum bool hasValue(alias fun) = !is(ReturnType!(fun) == void); --------------------

template which specifies how functions will be implemented/overridden. Two arguments are passed to how: the type Base and an alias to an implemented function. Then how must return an implemented function body as a string. The generated function body can use these keywords:

a0, a1, …: arguments passed to the function;
args: a tuple of the arguments;
self: an alias to the function itself;
parent: an alias to the overridden function (if any).

You may want to use templated property functions (instead of Implicit Template Properties) to generate complex functions: -------------------- // Prints log messages for each call to overridden functions. string generateLogger(C, alias fun)() @property { import std.traits; enum qname = C.stringof ~ "." ~ _traits(identifier, fun); string stmt; stmt ~= q{ struct Importer { import std.stdio; } }; stmt ~= Importer.writeln("Log: ~ qname ~ (", args, ")");; static if (!_traits(isAbstractFunction, fun)) { static if (is(ReturnType!fun == void)) stmt ~= q{ parent(args); }; else stmt ~= q{ auto r = parent(args); Importer.writeln("--> ", r); return r; }; } return stmt; } --------------------

what template which determines what functions should be implemented/overridden. An argument is passed to what: an alias to a non-final member function in Base. Then what must return a boolean value. Return true to indicate that the passed function should be implemented/overridden. -------------------- // Sees if fun returns something. enum bool hasValue(alias fun) = !is(ReturnType!(fun) == void); --------------------

Note

Generated code is inserted in the scope of std.typecons module. Thus, any useful functions outside std.typecons cannot be used in the generated code. To workaround this problem, you may import necessary things in a local struct, as done in the generateLogger() template in the above example.

BUGS

Variadic arguments to constructors are not forwarded to super.
Deep interface inheritance causes compile error with messages like

"Error: function std.typecons.AutoImplement!(Foo).AutoImplement.bar does not override any function". [Bugzilla 2525, Bugzilla 3525]
The parent keyword is actually a delegate to the super class' corresponding member function. [Bugzilla 2540]
Using alias template parameter in how and/or what may cause strange compile error. Use template tuple parameter instead to workaround this problem. [Bugzilla 4217]

Class `std.typecons.AutoImplement`

Inherits from

Methods

Parameters

Note

BUGS

Authors

License

Comments

Class std.typecons.AutoImplement

Inherits from

Methods

Parameters

Note

BUGS

Authors

License

Comments

Class `std.typecons.AutoImplement`