I am trying to convert a struct to a string using the standard library's json package, but i am getting an error saying type 'type' does not support field access which is coming from the json.stringify's definition.
#How to use the zig's JSON stringify function.
hearty totem
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my attempt to call the function.
silver flare
You need to pass in a value of Block to stringify instead of the type itself
hearty totem
True!!, but still have the same issue.
hearty totem
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this..
silver flare
Im gonna guess it has to do with data
You need to pass in an impl of std.io.Writer for the third parameter
Easiest way is to change data to a std.ArrayList of u8, then pass in list.writer() for the third parameter (im on mobile so sorry I can’t write an example for ya 😅)
hearty totem
Easiest way is to change data to a std.ArrayList of u8, then pass in list.writer...
will try this..
silver flare
What’s Json? Is that an alias for std.json or?
hearty totem
yea, it's just an alias for std.json
silver flare
Ah okay
const std = @import("std");
const Point = struct {
x: i32,
y: i32,
};
pub fn main() !void {
var point = Point{ .x = 1, .y = 2 };
var serialized = std.ArrayList(u8).init(std.heap.page_allocator);
defer serialized.deinit();
try std.json.stringify(point, .{}, serialized.writer());
std.debug.print("{s}\n", .{serialized.items});
}
something like this should work for ya
hearty totem
Oh okay, let me try this.
tried with your sample code, it worked on var point = .{ .x = 1, .y = 2 } but doesn't work with my struct.
silver flare
What’s your type look like? It may have a field that std.json doesn’t know how to serialize
hearty totem
just playing around with Block definitions.
silver flare
Yeah allocator’s got a bunch of weird stuff in it that std.json doesnt know how to handle
You can pass in an anonymous struct literal with just the fields you wan
.{ .prevHash = self.prevHash, … }
That’d be one way
silver flare
Can you comment out the hashing code and see if you still get that?
silver flare
Hm, should be working then
You’re setting all the struct fields to have values right?
hearty totem
not all of them tho.
by default i am setting some of them to be undefined.
that doesn't count as a value, does it?
silver flare
It does yeah, but you generally shouldn’t do that. Undefined’s kinda scary cause you can get segfaults like that
Better to leave them with no initial value or make them optional and have a default value of null
Or you can just give them a default value
silver flare
No problem!