conditional

Documentation

Overview

Package conditional Conditional Expression Operators

Index

• func Cond[T expression.AnyExpression](fieldName string, ifExpr T, thenExpr, elseExpr T) conditionalOperator
• func IfNull[T expression.AnyExpression](fieldName string, es []T, replace T) conditionalOperator
• func Switch[T expression.AnyExpression](fieldName string, branches []Branch[T], defaultExpr T) conditionalOperator
• type Branch

Functions

func Cond

func Cond[T expression.AnyExpression](fieldName string, ifExpr T, thenExpr, elseExpr T) conditionalOperator

Cond Evaluates a boolean expression to return one of the two specified return expressions. The $cond expression has one of two syntaxes: { $cond: { if: <boolean-expression>, then: <true-case>, else: <false-case> } } Or: { $cond: [ <boolean-expression>, <true-case>, <false-case> ] } $cond requires all three arguments (if-then-else) for either syntax. If the <boolean-expression> evaluates to true, then $cond evaluates and returns the value of the <true-case> expression. Otherwise, $cond evaluates and returns the value of the <false-case> expression. The arguments can be any valid expression.

func IfNull

func IfNull[T expression.AnyExpression](fieldName string, es []T, replace T) conditionalOperator

IfNull Changed in version 5.0. The $ifNull expression evaluates input expressions for null values and returns: The first non-null input expression value found. A replacement expression value if all input expressions evaluate to null. $ifNull treats undefined values and missing fields as null. Syntax:

{
  $ifNull: [
     <input-expression-1>,
     ...
     <input-expression-n>,
     <replacement-expression-if-null>
  ]
}

In MongoDB 4.4 and earlier versions, $ifNull only accepts a single input expression:

{
  $ifNull: [
     <input-expression>,
     <replacement-expression-if-null>
  ]
}

func Switch

func Switch[T expression.AnyExpression](fieldName string, branches []Branch[T], defaultExpr T) conditionalOperator

Switch Evaluates a series of case expressions. When it finds an expression which evaluates to true, $switch executes a specified expression and breaks out of the control flow. $switch has the following syntax:

$switch: {
  branches: [
     { case: <expression>, then: <expression> },
     { case: <expression>, then: <expression> },
     ...
  ],
  default: <expression>
}

The objects in the branches array must contain only a case field and a then field.

Types

type Branch

type Branch[T expression.AnyExpression] struct {
	Case T
	Then T
}