Aggregation Expression - $arrayElemAt

Function Build

Build $arrayElemAt with the ArrayElemAt function from the aggregation package.

// bson.D{bson.E{Key:"firstTag", Value:bson.D{bson.E{Key:"$arrayElemAt", Value:[]interface {}{"$tags", 0}}}}}
result := aggregation.ArrayElemAt("firstTag", "$tags", 0)

Method Build (Builder)

Build $arrayElemAt with the ArrayElemAt method from aggregation.NewBuilder().

// bson.D{bson.E{Key:"firstTag", Value:bson.D{bson.E{Key:"$arrayElemAt", Value:[]interface {}{"$tags", 0}}}}}
result := aggregation.NewBuilder().
    ArrayElemAt("firstTag", "$tags", 0).
    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.

ArrayElemAtWithoutKey

Function build:

// bson.D{bson.E{Key:"$arrayElemAt", Value:[]any{"$tags", 0}}}
expr := aggregation.ArrayElemAtWithoutKey("$tags", 0)

Method build (Builder):

// bson.D{bson.E{Key:"$arrayElemAt", Value:[]any{"$tags", 0}}}
expr := aggregation.NewBuilder().
    ArrayElemAtWithoutKey("$tags", 0).
    Build()