你可以用以下方法将其声明为nil:

var assoc : [String:String]

好的是你已经有了排版(注意我用了var和not let，把它们看成可变和不可变)然后你可以稍后再填写:

assoc = ["key1" : "things", "key2" : "stuff"]

var emptyDictionary = [String: String]()

var populatedDictionary = ["key1": "value1", "key2": "value2"]

注意:如果你打算改变字典的内容，那么就把它声明为一个变量(var)。你可以将一个空字典声明为常量(let)，但如果你想要改变它，这将是毫无意义的，因为常量值在初始化后不能被改变。

它很方便你找路

var dict:Dictionary = [:]

Swift文档推荐用以下方式初始化一个空Dictionary:

var emptyDict = [String: String]()

当我第一次遇到这个问题时，我有点困惑，因为不同的答案显示了初始化空Dictionary的不同方法。事实证明，实际上有很多方法可以做到这一点，尽管考虑到Swift推断类型的能力，有些方法有点冗余或过于冗长。

var emptyDict = [String: String]()
var emptyDict = Dictionary<String, String>()
var emptyDict: [String: String] = [:]
var emptyDict: [String: String] = [String: String]()
var emptyDict: [String: String] = Dictionary<String, String>()
var emptyDict: Dictionary = [String: String]()
var emptyDict: Dictionary = Dictionary<String, String>()
var emptyDict: Dictionary<String, String> = [:]
var emptyDict: Dictionary<String, String> = [String: String]()
var emptyDict: Dictionary<String, String> = Dictionary<String, String>()

在你有一个空字典之后，你可以像这样添加一个键值对:

emptyDict["some key"] = "some value"

如果你想再次清空你的字典，你可以做以下事情:

emptyDict = [:]

类型仍然是<String, String>，因为这是它初始化的方式。

在Swift中声明和初始化字典

字符串字典

var stringDict: [String: String] = [String: String]()

OR

var stringDict: Dictionary<String, String> = Dictionary<String, String>()

Int字典

var stringDict: [String: Int] = [String: Int]()

OR

var stringDict: Dictionary<String, Int> = Dictionary<String, Int>()

AnyObject字典

var stringDict: [String: AnyObject] = [String: AnyObject]()

OR

var stringDict: Dictionary<String, AnyObject> = Dictionary<String, AnyObject>()

字符串数组字典

var stringDict: [String: [String]] = [String: [String]]()

OR

var stringDict: Dictionary<String, Array<String>> = Dictionary<String, Array<String>>()

字符串字典数组

var stringDict: [[String: String]] = [[String: String]]()

OR

var stringDict: Array<Dictionary<String, String>> = Array<Dictionary<String, String>>()

斯威夫特4

let dicc = NSDictionary()

//MARK: - This is empty dictionary
let dic = ["":""]

//MARK:- This is variable dic means if you want to put variable 
let dic2 = ["":"", "":"", "":""]

//MARK:- Variable example
let dic3 = ["name":"Shakeel Ahmed", "imageurl":"https://abc?abc.abc/etc", "address":"Rawalpindi Pakistan"]

//MARK: - This is 2nd Variable Example dictionary
let dic4 = ["name": variablename, "city": variablecity, "zip": variablezip]

//MARK:- Dictionary String with Any Object
var dic5a = [String: String]()
//MARK:- Put values in dic
var dic5a = ["key1": "value", "key2":"value2", "key3":"value3"]

var dic5b = [String:AnyObject]()
dic5b = ["name": fullname, "imageurl": imgurl, "language": imgurl] as [String : AnyObject]

or
//MARK:- Dictionary String with Any Object
let dic5 = ["name": fullname, "imageurl": imgurl, "language": imgurl] as [String : AnyObject]

//MARK:- More Easy Way
let dic6a = NSDictionary()
let dic6b = NSMutalbeDictionary()