Struct UpdateSetRhs 

pub struct UpdateSetRhs<'a>(/* private fields */);

Advanced right-hand-side expression builder for DynamoDB SET actions.

UpdateSetRhs<'a> represents the right-hand side of a SET attr = <rhs> expression. It is used with Update::set_custom when the simple Update::set shorthand is insufficient — for example, when you need to reference another attribute, use if_not_exists, or build complex arithmetic expressions.

UpdateSetRhs values can be combined with + and - to ease building of arithmetic expressions:

use dynamodb_facade::{Update, UpdateSetRhs};

// SET score = other_score + 10
let rhs = UpdateSetRhs::attr("other_score") + UpdateSetRhs::value(10);
let update = Update::set_custom("score", rhs);
assert_eq!(format!("{update}"), r#"SET score = other_score + N("10")"#);

// SET balance = base_balance - penalty
let rhs = UpdateSetRhs::attr("base_balance") - UpdateSetRhs::attr("penalty");
let update = Update::set_custom("balance", rhs);
assert_eq!(format!("{update}"), "SET balance = base_balance - penalty");

Implementations

impl<'a> UpdateSetRhs<'a>

pub fn value(value: impl IntoAttributeValue) -> Self

Creates an RHS that reference a literal value.

This is the simplest form. For most cases, Update::set is more ergonomic and equivalent.

Examples

use dynamodb_facade::{Update, UpdateSetRhs};

let update = Update::set_custom("score", UpdateSetRhs::value(100));
assert_eq!(format!("{update}"), r#"SET score = N("100")"#);

// Same as Update::set
let update = Update::set("score", 100);
assert_eq!(format!("{update}"), r#"SET score = N("100")"#);

pub fn attr(attr: impl Into<Cow<'a, str>>) -> Self

Creates an RHS that references another attribute by name.

Use this to copy one attribute’s value to another, or as part of an arithmetic expression.

Examples

use dynamodb_facade::{Update, UpdateSetRhs};

// SET old_score = current_score
let update = Update::set_custom("old_score", UpdateSetRhs::attr("current_score"));
assert_eq!(format!("{update}"), "SET old_score = current_score");

pub fn if_not_exists( attr: impl Into<Cow<'a, str>>, value: impl IntoAttributeValue, ) -> Self

Creates an RHS using if_not_exists(attr, default).

Evaluates to the current value of attr if it exists, or default otherwise. Useful for initializing an attribute on first write without overwriting an existing value.

Examples

use dynamodb_facade::{Update, UpdateSetRhs};

// SET old_score = if_not_exists(score, 0)
let update = Update::set_custom(
    "old_score",
    UpdateSetRhs::if_not_exists("score", 0),
);
assert_eq!(
    format!("{update}"),
    r#"SET old_score = if_not_exists(score, N("0"))"#
);

Trait Implementations

impl<'a> Add for UpdateSetRhs<'a>

Combines two RHS expressions with addition: expr1 + expr2.

Produces a expr1 + expr2 arithmetic expression fragment for use in a SET action.

Examples

use dynamodb_facade::{Update, UpdateSetRhs};

// SET score = base_score + 10
let update = Update::set_custom(
    "score",
    UpdateSetRhs::attr("base_score") + UpdateSetRhs::value(10),
);
assert_eq!(format!("{update}"), r#"SET score = base_score + N("10")"#);

// SET balance = base_balance + last_payment
let rhs = UpdateSetRhs::attr("base_balance") + UpdateSetRhs::attr("last_payment");
let update = Update::set_custom("balance", rhs);
assert_eq!(format!("{update}"), "SET balance = base_balance + last_payment");

type Output = UpdateSetRhs<'a>

The resulting type after applying the + operator.

fn add(self, rhs: UpdateSetRhs<'a>) -> Self::Output

Performs the + operation.

impl<'a> Clone for UpdateSetRhs<'a>

fn clone(&self) -> UpdateSetRhs<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for UpdateSetRhs<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Sub for UpdateSetRhs<'a>

Combines two RHS expressions with subtraction: expr1 - expr2.

Produces a expr1 - expr2 arithmetic expression fragment for use in a SET action.

Examples

use dynamodb_facade::{Update, UpdateSetRhs};

// SET balance = base_balance - 5
let update = Update::set_custom(
    "balance",
    UpdateSetRhs::attr("base_balance") - UpdateSetRhs::value(5),
);
assert_eq!(format!("{update}"), r#"SET balance = base_balance - N("5")"#);

// SET balance = base_balance - penalty
let rhs = UpdateSetRhs::attr("base_balance") - UpdateSetRhs::attr("penalty");
let update = Update::set_custom("balance", rhs);
assert_eq!(format!("{update}"), "SET balance = base_balance - penalty");

type Output = UpdateSetRhs<'a>

The resulting type after applying the - operator.

fn sub(self, rhs: UpdateSetRhs<'a>) -> Self::Output

Performs the - operation.