Filter data with condition in an array inside an array

Question

I need to fill in "cursos", an array that contains all those that meet the condition "idcarrera" in CursosAllG -> idcarrera == carreraEnSeleccion

class CursosG: NSObject, NSCoding {
    let id: Int
    let nrc: String
    let profesor: String
    let carrera: [CarrerasG]

    init(id: Int, nrc: String, profesor: String, carrera: [CarrerasG]) {
        self.id = id
        self.nrc = nrc
        self.profesor = profesor
        self.carrera = carrera
    }
}

class CarrerasG: NSObject, NSCoding {
    let idcarrera: Int
    let nombre: String
    let semestre: Int

    init(idcarrera: Int, nombre: String, semestre: Int) {
        self.idcarrera = idcarrera
        self.nombre = nombre
        self.semestre = semestre
    }     
}

...
var carreraEnSeleccion = 1
var CursosAllG = [CursosG]()
var cursos = [Int()]

...

cursos = CursosAllG.flatMap { $0.carrera.first.flatMap { $0.idcarrera == carreraEnSeleccion }! ? $0.id: nil }

But it throws me only a few results (almost always only the first ones in the array Carreras in CursosAllG) and not all those that really meet the condition.

Example ->

CursosAllG = [CursosG(id: 2, nrc: "1234", profesor: "Ross", carrera: [CarrerasG(idcarrera: 2, nombre: "ICI", semestre: 3), CarrerasG(idcarrera: 1, nombre: "ICCI", semestre: 3)]), CursosG(id: 3, nrc: "1234", profesor: "Eric", carrera: [CarrerasG(idcarrera: 2, nombre: "ICI", semestre: 4), CarrerasG(idcarrera: 1, nombre: "ICCI", semestre: 5)]), CursosG(id: 10, nrc: "1234", profesor: "Pelao", carrera: [CarrerasG(idcarrera: 2, nombre: "ICI", semestre: 10)]), CursosG(id: 13, nrc: "1234", profesor: "zandoval", carrera: [CarrerasG(idcarrera: 1, nombre: "ICCI", semestre: 10)])]

Answer 1

cursos = CursosAllG.flatMap {
    $0.carrera.first { $0.idcarrera == carreraEnSeleccion } == nil ? nil : $0.id
}