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Format

Formats values into a string using replacement fields.

Module: Std

Summary

Format(fmt: char8[], args: Display...) -> String

Description

Format creates a new string by replacing placeholder fields in a format string with the string representation of supplied arguments.

Arguments must implement the Display interface.

Each occurrence of {} is replaced by the next argument in the argument list.

Parameters

Parameter Description
fmt Format string containing zero or more {} placeholders.
args Values used to replace placeholders.

Return Value

Returns a newly allocated String containing the formatted result.

Placeholders

The following placeholder is supported:

{}

Each placeholder consumes one argument.

Example

let text = Format("Hello, {}!", name);

Result:

Hello, Alex!

Examples

Single Argument

let name = String::From("Alex");

let text = Format("Hello, {}!", name);

Result:

Hello, Alex!

Multiple Arguments

let text = Format(
    "{} scored {} points",
    playerName,
    score
);

Result:

Alex scored 42 points

No Placeholders

let text = Format("Hello World");

Result:

Hello World

Using Display

Any type implementing Display can be formatted.

struct Person {
    name: String;
}

extend Person : Display {
    func ToString(self) -> String {
        return self.name;
    }
}

let person = Person {
    name: String::From("Alex")
};

let text = Format("{}", person);

Result:

Alex

Notes

  • Arguments are formatted by calling ToString().
  • Placeholders are processed from left to right.
  • Extra arguments are ignored.
  • Missing arguments produce no output for the corresponding placeholder.
  • A new string is always returned.

See Also