如何在Zig中向函数传递stream或writer参数？

针对你在Zig 0.10.0中遇到的两个错误，分别给出修复方案：

错误1：'File' is not marked 'pub' #

print1函数参数使用的std.io.File并非公开可用类型，而std.io.getStdOut()返回的实际是std.fs.File类型。只需修正参数类型即可：

pub fn print1(file: std.fs.File, str: []const u8) !void {
    try file.writer().print("{s}", .{str});
}

错误2：expected type 'type', found 'fn(comptime type, comptime type, comptime anytype) type' #

std.io.Writer不是具体类型，而是用于构造Writer实例的泛型构造器。要让函数兼容任意符合Writer接口的对象，使用anytype泛型参数是最简洁的方式，Zig会自动推导类型并检查方法兼容性：

fn print2(writer: anytype, str: []const u8) !void {
    try writer.print("{s}", .{str});
}

若需要更严谨的类型约束，也可以明确指定Writer接口类型：

fn print2(writer: std.io.Writer(@TypeOf(writer.context), writer.Error, writer.write), str: []const u8) !void {
    try writer.print("{s}", .{str});
}

完整修复代码 #

const std = @import("std");
pub fn main() !void {
    try print1(std.io.getStdOut(), "Hello, ");
    try print2(std.io.getStdOut().writer(), "world!");
}

pub fn print1(file: std.fs.File, str: []const u8) !void {
    try file.writer().print("{s}", .{str});
}

fn print2(writer: anytype, str: []const u8) !void {
    try writer.print("{s}", .{str});
}

内容的提问来源于stack exchange，提问作者Adrian Savage