定义字典常量(常量只有读操作)
let dictionary1 = ["key1": 888, "key2": 999]
let dictionary2: [String: Int] = ["key1": 888, "key2": 999]
定义字典变量
var dictionary: [String:Int] = [:]
var dictionary1 = ["key1": 55, "key2": 555]
var dictionary2 = Dictionary<String, Int>()
赋值
dictionary = ["key1": 88, "key2":888, "key3": 8888]
取值
let value = dictionary["key1"] // 取某个值
let values = dictionary.values.sorted() // 获取所有value，从小到大排序
let keys = dictionary.keys.sorted() // 获取所有key，从小到大排序
修改value/添加元素
dictionary.updateValue(8, forKey: "key4") // 如果key不存在，则添加新元素
dictionary.updateValue(99, forKey: "key1")// 如果key存在，则修改value
删除元素
dictionary.removeAll() // 删除所有元素
dictionary.removeValue(forKey: "key1") // 通过查找key来删除元素
let index = dictionary.index(dictionary.startIndex, offsetBy: 1)
dictionary.remove(at: index) // 通过下标删除元素，offsetBy是第几个元素
字典遍历
for item in dictionary {
print("\(item.key) --> \(item.value)")
}
for (key, value) in dictionary {
print("\(key) --> \(value)")
}
for sequence in dictionary.enumerated() {
print("\(sequence.offset) --> \(sequence.element.key), \(sequence.element.value)")
}
for (offset, item) in dictionary.enumerated() {
print("\(offset) --> \(item.key), \(item.value)")
}
