Struct MessageSelector 

pub struct MessageSelector { /* private fields */ }

Selects messages at the server side based on filter expressions.

Supports two types of filtering:

• TAG: Simple tag-based filtering using || operator for multiple tags
• SQL92: Advanced SQL-like filtering with conditions on message properties

Examples

// Select by tag
let selector = MessageSelector::by_tag("TagA");

// Select by SQL92 expression
let selector = MessageSelector::by_sql("a > 10 AND b = 'value'");

Implementations

impl MessageSelector

pub fn by_sql(sql: impl Into<CheetahString>) -> Self

Creates a selector using SQL92 syntax for advanced filtering.

SQL92 filtering supports:

• Keywords: AND, OR, NOT, BETWEEN, IN, TRUE, FALSE, IS, NULL
• Data types: Boolean, String (quoted), Decimal, Float
• Operators: >, >=, <, <=, =
• Special operations:
  • BETWEEN A AND B (equivalent to >= A AND <= B)
  • IN ('a', 'b') (equivalent to = 'a' OR = 'b')
  • IS NULL, IS NOT NULL

Arguments

• sql - SQL92 filter expression. If None, empty, or "*", selects all messages.

Examples

let selector =
    MessageSelector::by_sql("(price > 100 AND category = 'electronics') OR discount = true");

pub fn by_tag(tag: impl Into<CheetahString>) -> Self

Creates a selector using tag-based filtering.

Tag filtering supports multiple tags separated by || (OR operation).

Arguments

• tag - Tag expression. If None, empty, or "*", selects all messages.

Examples

// Single tag
let selector = MessageSelector::by_tag("TagA");

// Multiple tags (OR operation)
let selector = MessageSelector::by_tag("TagA || TagB || TagC");

// Subscribe all
let selector = MessageSelector::by_tag("*");

pub fn get_expression_type(&self) -> &CheetahString

Returns the expression type (“TAG” or “SQL92”).

pub fn get_expression(&self) -> &CheetahString

Returns the filter expression content.

Trait Implementations

impl Clone for MessageSelector

fn clone(&self) -> MessageSelector

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MessageSelector

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

Formats the value using the given formatter.

impl PartialEq for MessageSelector

fn eq(&self, other: &MessageSelector) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for MessageSelector