Retirar y elemento de la matriz Firebase Swift 5
let washingtonRef = db.collection("cities").document("DC")
// Atomically add a new region to the "regions" array field.
washingtonRef.updateData([
"regions": FieldValue.arrayUnion(["greater_virginia"])
])
// Atomically remove a region from the "regions" array field.
washingtonRef.updateData([
"regions": FieldValue.arrayRemove(["east_coast"])
])
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