Macro format_xml::template

macro_rules! template {
    ($($tt:tt)*) => { ... };
}

Template strings.

Compiles down to a single format_args! invocation.

Examples

Basic usage

let name = "World";

template!("Hello "{name}"!").to_string()

The resulting string is Hello World!.

Note how the expression values to be formatted are inlined in the formatting braces. Due to limitations of declarative macros the formatting braces are not part of the surrounding string literals.

Formatting specifiers

let value = 42;

template!("hex("{value}") = "{value;#x}).to_string()

The resulting string is hex(42) = 0x2a.

Due to limitations of declarative macros, a semicolon is used to separate the value from the formatting specifiers. The rules for the specifiers are exactly the same as Rust's standard formatting syntax.

Control flow

let switch = true;
let opt = Some("World");
let result: Result<f32, i32> = Err(13);

template! {
	if let Some(name) = (opt) {
		"# Hello " {name}"\n\n"
	}
	else if (switch) {
		"# Hello User\n\n"
	}
	if (switch) {
		"Message: "
		match (result) {
			Ok(f) => { "_"{f}"_\n\n" }
			Err(i) => { "**"{i}"**\n\n" }
		}
		for i in (1..=5) {
			let times_five = i * 5;
			"* "{i}" x 5 = "{times_five}"\n"
		}
	}
	else {
		"No contents"
	}
}.to_string()

The resulting string is # Hello World\n\nMessage: **13**\n\n* 1 x 5 = 5\n* 2 x 5 = 10\n* 3 x 5 = 15\n* 4 x 5 = 20\n* 5 x 5 = 25\n.

Custom formatting

template! { |f| {
	f.write_str("custom formatting")
}}.to_string()

If all else fails the closure syntax enables to write custom formatting code. The signature is the same as the fmt method of Rust's standard formatting traits.

f is &mut Formatter and the closure returns a Result.