std::fmt::Formatter - Rust
Description: API documentation for the Rust `Formatter` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Formatter

# Struct std::fmt::Formatter 1.0.0 [−] [src]

    pub struct Formatter<'a> { /* fields omitted */ }

A struct to represent both where to emit formatting strings to and how they should be formatted. A mutable version of this is passed to all formatting traits.

## Methods

### `impl<'a> Formatter<'a>`
[src]

#### `fn pad_integral(&mut self,
is_nonnegative: bool,
prefix: &str,
buf: &str)
-> Result<(), Error>`

Performs the correct padding for an integer which has already been emitted into a str. The str should not contain the sign for the integer, that will be added by this method.

# Arguments

- is_nonnegative - whether the original integer was either positive or zero.
- prefix - if the '#' character (Alternate) is provided, this is the prefix to put in front of the number.
- buf - the byte array that the number has been formatted into

This function will correctly account for the flags provided as well as the minimum width. It will not take precision into account.

#### `fn pad(&mut self, s: &str) -> Result<(), Error>`

This function takes a string slice and emits it to the internal buffer after applying the relevant formatting flags specified. The flags recognized for generic strings are:

- width - the minimum width of what to emit
- fill/align - what to emit and where to emit it if the string provided needs to be padded
- precision - the maximum length to emit, the string is truncated if it is longer than this length

Notably this function ignored the `flag` parameters

#### `fn write_str(&mut self, data: &str) -> Result<(), Error>`

Writes some data to the underlying buffer contained within this formatter.

#### `fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>`

Writes some formatted information into this instance

#### `fn flags(&self) -> u32`

Flags for formatting (packed version of rt::Flag)

#### `fn fill(&self) -> char`
1.5.0

Character used as 'fill' whenever there is alignment

#### `fn align(&self) -> Alignment`

🔬 This is a nightly-only experimental API. (`fmt_flags_align` #27726)

method was just created

Flag indicating what form of alignment was requested

#### `fn width(&self) -> Option<usize>`
1.5.0

Optionally specified integer width that the output should be

#### `fn precision(&self) -> Option<usize>`
1.5.0

Optionally specified precision for numeric types

#### `fn sign_plus(&self) -> bool`
1.5.0

Determines if the `+` flag was specified.

#### `fn sign_minus(&self) -> bool`
1.5.0

Determines if the `-` flag was specified.

#### `fn alternate(&self) -> bool`
1.5.0

Determines if the `#` flag was specified.

#### `fn sign_aware_zero_pad(&self) -> bool`
1.5.0

Determines if the `0` flag was specified.

#### `fn debug_struct(&'b mut self, name: &str) -> DebugStruct<'b, 'a>`
1.2.0

Creates a `DebugStruct` builder designed to assist with creation of `fmt::Debug` implementations for structs.

# Examples

    use std::fmt;

    struct Foo {
        bar: i32,
        baz: String,
    }

    impl fmt::Debug for Foo {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_struct("Foo")
                .field("bar", &self.bar)
                .field("baz", &self.baz)
                .finish()
        }
    }

    // prints "Foo { bar: 10, baz: "Hello World" }"
    println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });Run

#### `fn debug_tuple(&'b mut self, name: &str) -> DebugTuple<'b, 'a>`
1.2.0

Creates a `DebugTuple` builder designed to assist with creation of `fmt::Debug` implementations for tuple structs.

# Examples

    use std::fmt;

    struct Foo(i32, String);

    impl fmt::Debug for Foo {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_tuple("Foo")
                .field(&self.0)
                .field(&self.1)
                .finish()
        }
    }

    // prints "Foo(10, "Hello World")"
    println!("{:?}", Foo(10, "Hello World".to_string()));Run

#### `fn debug_list(&'b mut self) -> DebugList<'b, 'a>`
1.2.0

Creates a `DebugList` builder designed to assist with creation of `fmt::Debug` implementations for list-like structures.

# Examples

    use std::fmt;

    struct Foo(Vec<i32>);

    impl fmt::Debug for Foo {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_list().entries(self.0.iter()).finish()
        }
    }

    // prints "[10, 11]"
    println!("{:?}", Foo(vec![10, 11]));Run

#### `fn debug_set(&'b mut self) -> DebugSet<'b, 'a>`
1.2.0

Creates a `DebugSet` builder designed to assist with creation of `fmt::Debug` implementations for set-like structures.

# Examples

    use std::fmt;

    struct Foo(Vec<i32>);

    impl fmt::Debug for Foo {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_set().entries(self.0.iter()).finish()
        }
    }

    // prints "{10, 11}"
    println!("{:?}", Foo(vec![10, 11]));Run

#### `fn debug_map(&'b mut self) -> DebugMap<'b, 'a>`
1.2.0

Creates a `DebugMap` builder designed to assist with creation of `fmt::Debug` implementations for map-like structures.

# Examples

    use std::fmt;

    struct Foo(Vec<(String, i32)>);

    impl fmt::Debug for Foo {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
        }
    }

    // prints "{"A": 10, "B": 11}"
    println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));Run

## Trait Implementations

### `impl<'a> Write for Formatter<'a>`
1.2.0
[src]

#### `fn write_str(&mut self, s: &str) -> Result<(), Error>`

Writes a slice of bytes into this writer, returning whether the write succeeded. Read more

#### `fn write_char(&mut self, c: char) -> Result<(), Error>`

Writes a `char` into this writer, returning whether the write succeeded. Read more

#### `fn write_fmt(&mut self, args: Arguments) -> Result<(), Error>`

Glue for usage of the `write!` macro with implementors of this trait. Read more

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