编辑代码

//20190401031杨小可

//student's information
var name: String = "Tommy"
var hobby: String?
//force unwrapping
if hobby != nil {
    print("\(name)'s hobby is \(hobby)")
} else {
    print("\(name) has no hobby")
}

var membership: String?
membership="IEEE senior member"
//optional binding
if let membership = membership {
    print("\(name) is \(membership) ")
}else{
    print("\(name) doesn't join any orginization!")
}

//multiple optional binding
hobby = "soccer"
if let membership = membership, let hobby = hobby{
    print("\(name)'s hobby is \(hobby) and is also \(membership)")
}else{
    print("\(name) has no hobby or doesn't join any orgnization!")
}