//MARK:----------字典--------------
/* 字典（key : value）*/
//如果类型信息已知，使用[:]声明空字典。
let emptyDictionary1 = [:]
let emptyDictionary2 = Dictionary<String,Float>()
let emptyDictionary3 = [String: Float]()
print(emptyDictionary2.count)

//var airports: Dictionary<String,String> = ["TYO": "Tokyo","DUB": "Dublin"]
var airportsDic = ["TYO": "Tokyo","DUB": "Dublin"]
print(airportsDic["TYO"])

//---------添加----------
airportsDic["LHR"] = "London"
print(airportsDic)
//-------修改------
airportsDic["LHR"] = "London Heathrow" // the value for "LHR" has been changed to "London Heathrow
print(airportsDic)
//等价于
//airports.updateValue("Dublin International",forKey: "DUB")
//print(airports)

//------------删除-----------
airportsDic["LHR"] = nil
print(airportsDic)
//等价于
//airportsDic("DUB")
//print(airportsDic)

//---------查询----------
print("字典元素个数为" + String(airportsDic.count))
print("字典包含 \(airportsDic.count) 个元素.")

print(airportsDic.startIndex)
print(airportsDic.endIndex)


//-------------遍历字典-----------
for (key,Value) in airportsDic
{
    print("\(key): \(Value)")
}

for key in airportsDic.keys
{
    print("Airport code: \(key)")
}

for Value in airportsDic.values
{
    print("Airport name: \(Value)")
}

let airportKeys = Array(airportsDic.keys)     // airportCodes is ["TYO","LHR"]
let airportValues = Array(airportsDic.values)   // airportNames is ["Tokyo","London Heathrow"]
print(airportKeys)
print(airportValues)