Hi
I have solved this issue but it seems very strange from a syntax point of view. I have tested in stable 12 and 13. Both have the same results.
I need to add _:Self to the input parm of a struct function to get it to work. Otherwise it does not compile as a member function.
You get
problem_struct.zig:21:7: note: 'print4' is not a member function
pub fn print4 () void { std.debug.print("{s}, \n", .{Self.array[0]}); }
While this works fine
pub fn print3 (_:Self) void { std.debug.print("{s}, \n", .{Self.array[0]}); }
I understand why this works, from a compile point of view. But from a new coders point of view its weird that you have to declare something, Throw it away. So you can use it.
I guess I am asking whether anyone agrees? Is there a better way to enforce a function, which is defined in a struct, becomes a member function of the very struct it is defined in? Or do we do this for the greater good… the greater good. Grin
This is my first post so free to ignore.
All the best.
In my struct I have the following code extract
13 // works. I invoke self, throw it away to _, then use it
14 pub fn print3 (_:Self) void { std.debug.print("{s}, \n", .{Self.array[0]}); }
15 // does not work (but compiles if not called, I assume because of the lazy compile)
16 pub fn print4 () void { std.debug.print("{s}, \n", .{Self.array[0]}); }
The calling code extract
16 // run a public function of the object
17 my_object.print3();
18
19 // will not work, error below even though it is almost identical
20 my_object.print4();
The error
23 problem.zig:19:10: error: no field or member function named 'print4' in 'problem_struct.CreateStruct1(u8)'
24 my_object.print4();
25 ~~~~~~~~~^~~~~~~
26 problem_struct.zig:9:10: note: struct declared here
27 return struct {
28 ^~~~~~
29 **problem_struct.zig:21:7: note: 'print4' is not a member function**
30 pub fn print4 () void { std.debug.print("{s}, \n", .{Self.array[0]}); }
My understanding is that _=variable simply throws it away. ie send to /dev/null. But then I use it.
The code in full
cat problem.zig
// This is the calling code and is in the file problem.zig
const std = @import("std"); // get the standard lib
const Mystruct = @import("problem_struct.zig").CreateStruct1;
pub fn main() void
{
//create a struct with type u8 in memory by running the function
const build_my_struct=Mystruct(u8);// _=build_my_struct;
// create my object with fresh struct data from the u8 struct above
const my_object=build_my_struct.new(10);//_= my_object;
// run a public function of the object
my_object.print3();
// will not work, error below even though it is almost identical
my_object.print4();
} // end of main
The Struct function
cat problem_struct.zig
// this code is stored in the file problem_struct.zig
const std = @import("std"); // get the standard lib
pub fn CreateStruct1(comptime mytype: type) type
{
return struct {
const Self = @This();
const array=[_][]const u8{"hello","This is a test"};
// works
pub fn print3 (_:Self) void { std.debug.print("{s}, \n", .{Self.array[0]}); }
// does not
pub fn print4 () void { std.debug.print("{s}, \n", .{Self.array[0]}); }
// support to create the struct
pub fn new(x:mytype) Self {return .{.x_co=x};} // namespace function ie self:
x_co: mytype = 0, // random member
}; // end of struct
} // end of fn
