Easy solution for all your zig dynamic dispatch needs!
- Fully decoupled interfaces and implementations
- Control over the storage/ownership of interface objects
- Comptime support (including comptime-only interfaces)
- Async function partial support (blocking on #4621)
- Optional function support
- Support for manually written vtables
const interface = @import("interface.zig");
const Interface = interface.Interface;
const SelfType = interface.SelfType;
// Let us create a Reader interface.
// We wrap it in our own struct to make function calls more natural.
const Reader = struct {
pub const ReadError = error { CouldNotRead };
const IFace = Interface(struct {
// Our interface requires a single non optional, non-const read function.
read: fn (*SelfType, buf: []u8) ReadError!usize,
}, interface.Storage.NonOwning); // This is a non owning interface, similar to Rust dyn traits.
iface: IFace,
// Wrap the interface's init, since the interface is non owning it requires no allocator argument.
pub fn init(impl_ptr: var) Reader {
return .{ .iface = try IFace.init(.{impl_ptr}) };
}
// Wrap the read function call
pub fn read(self: *Reader, buf: []u8) ReadError!usize {
return self.iface.call("read", .{buf});
}
// Define additional, non-dynamic functions!
pub fn readAll(self: *Self, buf: []u8) ReadError!usize {
var index: usize = 0;
while (index != buf.len) {
const partial_amt = try self.read(buffer[index..]);
if (partial_amt == 0) return index;
index += partial_amt;
}
return index;
}
};
// Let's create an example reader
const ExampleReader = struct {
state: u8,
// Note that this reader cannot return an error, the return type
// of our implementation functions only needs to coerce to the
// interface's function return type.
pub fn read(self: ExampleReader, buf: []u8) usize {
for (buf) |*c| {
c.* = self.state;
}
return buf.len;
}
};
test "Use our reader interface!" {
var example_reader = ExampleReader{ .state=42 };
var reader = Reader.init(&example_reader);
var buf: [100]u8 = undefined;
_ = reader.read(&buf) catch unreachable;
}
See examples.zig for more examples.