Learning Swift from scratch (day 16)--Dictionary collection

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Swift A dictionary represents a very complex collection that allows the element to be accessed by a key. A dictionary is a set of two parts, one is a set of key (key), andThe other is a collection of values (value). A key collection cannot have duplicate elements, and a collection of values can be duplicated, and the keys and values are paired.

Dictionary Declaration and initialization

Swift Dictionary type is Dictionary , which is also a generic collection.

in declaring a Dictionary type, you can use one of the following statements.

var studentdictionary1:dictionary<int, String>var StudentDictionary2: [int:string]

The dictionary of the Declaration needs to be initialized to be used, and the dictionary type is often initialized at the same time as the declaration. The sample code is as follows:

var studentdictionary1:dictionary<int, string> = [102: "Zhang San", 105: "John Doe", 109: "Harry"]var StudentDictionary2 = [102: "Zhang San", 105: "John Doe", 109: "Harry"] let StudentDictionary3 =[102: "Zhang San", 105: "John Doe", 109: "Harry"]

Dictionary traversal

The dictionary traversal process can traverse only the collection of values, or only the collection of keys, or it can traverse at the same time. These traversal processes are implemented through the for-in Loop.

The following is a sample code that iterates through a dictionary:

var studentdictionary =[102: "Zhang San", 105: "John Doe", 109: "Harry"] print ("---traversal key---") for StudentID Instudentdictionary.keys {pri NT ("study number: \ (StudentID)")} print ("---traverse value---") for studentname instudentdictionary.values {print ("Student: \ (Studentname)")} Print ("---traversal key: Value---") for (Studentid,studentname) in Studentdictionary {print ("\ (StudentID): \ (Studentname)}}

The results of the operation are as follows:

--- Traverse Key ---

School Number: the

School Number: 102

School Number: 109

--- Traversing Values ---

Student: John Doe

Student: Zhang San

Student: Harry

--- Traverse Key : value ---

: John Doe

102: Zhang San

109: Harry

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Learning Swift from scratch (day 16)--Dictionary collection