Aggregation Expression - $ifNull

Function Build

Build $ifNull with the IfNull function from the aggregation package.

// bson.D{bson.E{Key:"displayName", Value:bson.D{bson.E{Key:"$ifNull", Value:[]interface {}{"$nickname", "$name"}}}}}
result := aggregation.IfNull("displayName", "$nickname", "$name")

Method Build (Builder)

Build $ifNull with the IfNull method from aggregation.NewBuilder().

// bson.D{bson.E{Key:"displayName", Value:bson.D{bson.E{Key:"$ifNull", Value:[]interface {}{"$nickname", "$name"}}}}}
result := aggregation.NewBuilder().
    IfNull("displayName", "$nickname", "$name").
    Build()

Build Without Key

When an expression needs to be passed as an argument to another expression, use a WithoutKey variant to build an expression fragment without an output field name.

IfNullWithoutKey

Function build:

// bson.D{bson.E{Key:"$ifNull", Value:[]any{"$nickname", "anonymous"}}}
expr := aggregation.IfNullWithoutKey("$nickname", "anonymous")

Method build (Builder):

// bson.D{bson.E{Key:"$ifNull", Value:[]any{"$nickname", "anonymous"}}}
expr := aggregation.NewBuilder().
    IfNullWithoutKey("$nickname", "anonymous").
    Build()