Swift 基础学习(字典)

//(9)字典的概念和定义(key:value)

//哈希查找
//addr = hash(key), value = hashTable[addr]
//key一定是可hash的,String/Int/Float/Bool都是遵守hash的
var dic = [:]
dic = [1:"1", 2:"2"]
var dic1 = ["1":"1","2":"2"]
var dic2 = ["1":1, "2":2]
print(dic)
print(dic1)
print(dic2)
var dic3: Dictionary<String, Int> = ["3":3]
var dic4: [String: Int] = ["3":3]
print(dic3)
print(dic4)
print(dic.count)

//(10)字典的操作

var dict = ["apple":"苹果", "bag":"包"]
print(dict["apple"])
//修改某个值
dict["apple"] = "香蕉"
print(dict["apple"])
//更新某个值
dict.updateValue("苹果", forKey: "apple")
print(dict)
//如果键值对应经在字典中,那么会更新键值对;如果不存在相应的键值对,那么这个键值对会被加到字典中同时返回一个nil
//存在的情况
if let orig = dict.updateValue("苹果", forKey: "apple"){
print(dict["apple"])
print("==\(orig)")
print(dict)
}
//不存在的情况,字典中会多出一个键值对
if let orig1 = dict.updateValue("草莓", forKey: "appl"){
print(dict["apple"])
print("==\(orig1)")
}
print(dict)
//添加一个元素
dict["an"] = "一个"
print(dict)
//删除一个元素,返回一个之前key对应的值
if let old = dict.removeValueForKey("an") {
print(old)
}
print(dict)
//删除所有
//dict.removeAll(keepCapacity: true)

//(11)字典的遍历

for (key, value) in dict {
print("\(key): \(value)")
}
//打印所有的key
for key in dict.keys {
print(key)
}
//打印所有的value
for value in dict.values {
print(value)
}