Trait Expressive 

pub trait Expressive<T> {
    // Required method
    fn expr(&self) -> Expression<T>;

    // Provided method
    fn preview(&self) -> String
       where T: Debug + Display { ... }
}

Trait for creating custom SQL constructs that can be converted to expressions.

The Expressive trait allows you to define reusable SQL patterns and complex query constructs that can be seamlessly integrated into larger expressions. This is particularly useful for creating database-specific syntax, common query patterns, or complex operations like identifiers with automatic escaping.

Example

Create a wrapper for table/field names which will escape only if we use a reserved keyword.

use vantage_expressions::{Expression, expr};
use vantage_expressions::traits::expressive::Expressive;

#[derive(Debug, Clone)]
pub struct Identifier {
    identifier: String,
}

impl Identifier {
    pub fn new(identifier: impl Into<String>) -> Self {
        Self { identifier: identifier.into() }
    }

    fn needs_escaping(&self) -> bool {
        let reserved_keywords = ["SELECT", "FROM", "TO", "IN"];
        let upper = self.identifier.to_uppercase();
        self.identifier.contains(' ') || reserved_keywords.contains(&upper.as_str())
    }
}

impl Expressive<serde_json::Value> for Identifier {
    fn expr(&self) -> Expression<serde_json::Value> {
        if self.needs_escaping() {
            expr!(format!("`{}`", self.identifier))
        } else {
            expr!(self.identifier.clone())
        }
    }
}

// Usage - Expressive types work automatically in expr! macro
let field = Identifier::new("user_name");
let escaped = Identifier::new("SELECT"); // Reserved keyword

// Direct usage in expr! macro - no .expr() calls needed
let query = expr!(
    "SELECT {}, {}, {} FROM {}",
    (Identifier::new("from")),
    (Identifier::new("to")),
    (Identifier::new("subject")),
    (Identifier::new("emails"))
);
// Result: SELECT `from`, `to`, subject FROM emails

Required Methods

fn expr(&self) -> Expression<T>

Convert this construct into an Expression<T>.

This method should return an Expression that represents the SQL or query language construct. The expression can contain nested expressions, parameters, or deferred computations.

Types implementing this trait can be used directly in the expr! macro with parentheses syntax: (identifier) - the conversion happens automatically.

Provided Methods

fn preview(&self) -> String

where T: Debug + Display,

Preview the expression as a formatted string.

This method provides a convenient way to preview expressions without needing to call expr().preview() explicitly.

Implementations on Foreign Types

impl Expressive<bool> for bool

fn expr(&self) -> Expression<bool>

impl Expressive<f32> for f32

fn expr(&self) -> Expression<f32>

impl Expressive<f64> for f64

fn expr(&self) -> Expression<f64>

impl Expressive<i8> for i8

fn expr(&self) -> Expression<i8>

impl Expressive<i16> for i16

fn expr(&self) -> Expression<i16>

impl Expressive<i32> for i32

fn expr(&self) -> Expression<i32>

impl Expressive<i64> for i64

fn expr(&self) -> Expression<i64>

impl Expressive<u8> for u8

fn expr(&self) -> Expression<u8>

impl Expressive<u16> for u16

fn expr(&self) -> Expression<u16>

impl Expressive<u32> for u32

fn expr(&self) -> Expression<u32>

impl Expressive<AnySqliteType> for &str

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for bool

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for f32

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for f64

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for i8

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for i16

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for i32

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for i64

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for u8

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for u16

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for u32

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for String

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for DateTime<Utc>

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for NaiveDate

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for NaiveDateTime

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for NaiveTime

fn expr(&self) -> Expression<AnySqliteType>

impl Expressive<AnySqliteType> for Decimal

fn expr(&self) -> Expression<AnySqliteType>

impl<T> Expressive<T> for MockColumn<T>

where T: ColumnType,

fn expr(&self) -> Expression<T>

Implementors

impl Expressive<Value> for MockSelect

impl Expressive<AnySqliteType> for SqliteCondition

Condition chaining: the condition type wraps Expression<AnyType>, so implementing Expressive<AnyType> gives it the operation trait via the blanket above.

impl Expressive<AnySqliteType> for Concat<AnySqliteType>

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for DateFormat<AnySqliteType>

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for Identifier

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for Iif<AnySqliteType>

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for Interval

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for JsonExtract<AnySqliteType>

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for Point

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for Ternary<AnySqliteType>

Available on crate feature sqlite only.

impl Expressive<AnySqliteType> for SqliteDelete

impl Expressive<AnySqliteType> for SqliteInsert

impl Expressive<AnySqliteType> for SqliteSelect

impl Expressive<AnySqliteType> for SqliteUpdate

impl Expressive<AnySqliteType> for SqliteIdent

impl Expressive<AnySqliteType> for AnySqliteType

impl<'a, DS, T, R> Expressive<T> for AssociatedExpression<'a, DS, T, R>

where T: Clone, DS: ExprDataSource<T>,

impl<T> Expressive<T> for Column<T>

where T: ColumnType,

impl<T> Expressive<T> for Expression<T>

where T: Clone,

impl<T: Debug + Display + Clone> Expressive<T> for Case<T>

impl<T: Debug + Display + Clone> Expressive<T> for Fx<T>

impl<T: Debug + Display + Clone> Expressive<T> for Union<T>