typebox@0.32.21

0.17.6

Changes:

Added Type.Rec(...) function.

Notes:

This update introduces the Type.Rec() function for enabling Recursive Types. Please note that due to current inference limitations in TypeScript, TypeBox is unable to infer the type and resolves inner types to any.

This functionality enables for complex self referential schemas to be composed. The following creates a binary expression syntax node with the expression self referential for left and right operands.

const Operator = Type.Union([
    Type.Literal('+'),
    Type.Literal('-'),
    Type.Literal('/'),
    Type.Literal('*')
])

type Expression = Static<typeof Expression>

// Defines a self referencing type.
const Expression = Type.Rec(Self => Type.Object({
    left:     Type.Union([Self, Type.Number()]), 
    right:    Type.Union([Self, Type.Number()]),
    operator: Operator
}))

function evaluate(expression: Expression): number {
    const left = typeof expression.left  !== 'number' 
        ? evaluate(expression.left as Expression)  // assert as Expression
        : expression.left
    const right = typeof expression.right  !== 'number' 
        ? evaluate(expression.right as Expression) // assert as Expression
        : expression.right
    switch(expression.operator) {
        case '+': return left + right
        case '-': return left - right
        case '*': return left * right
        case '/': return left / right
    }
}

const result = evaluate({
    left: {
        left: 10, 
        operator: '*',
        right: 4, 
    },
    operator: '+',
    right: 2,
}) // -> 42

This functionality is flagged as EXPERIMENTAL and awaits community feedback.