More fun workarounds:
arrayObj += [(id: idInt, name: nameString)]
and
arrayObj.append([(id: idInt, name: nameString)][0])
Curiously, this works if you use a typealias:
typealias MyData = (id: Int, name: String)
var arrayObj: [MyData] = []
var idInt: Int = 1
var nameString: String = "hoge"
arrayObj.append((id: idInt, name: nameString))
EDIT:
One more workaround:
arrayObj.insert((id: idInt, name: nameString), atIndex:index)