Studying-swift:day02

Study Address: http://www.rm5u.com/or http://www.runoob.com/

1. Swift dictionary:
   • Create a dictionary:
   　　Create an empty dictionary of a specific type:
   var somedic = [keytype:valuetype] (): var somedic = [int:string] ()
         Create an instance of a dictionary:
   var somedic:[int:string] = [1: "one", 2: "one", 3: "three"]
   • Access Dictionaries:
   Access the array elements according to the index of the Dictionary:
   var Somevar = somedic[key]
   • Modify the Dictionary:
   You can use Updatevalue (forkey:) Add or update the contents of the Dictionary. If key does not exist, the value is added and if present, the value corresponding to the key is Modified. The Updatevalue (_:forkey:) method returns the optional Value.
   var oldval = Somedic.updatevalue ("new value of one", forkey:1)
   You can also modify the value of the dictionary by specifying the key
   somedic[1] = "new value of one"
   • Remove Key-value pairs:
   You can use the Removevalueforkey () method to remove a dictionary key-value pair. If the key exists, the method returns the removed value if no return nil exists
   You can also remove the Key-value (key-value) pair by specifying the value of the key as nil
   • Traverse the dictionary:
   You can use the for-in loop to traverse a key-value pair in a dictionary:
   

   = [1:"one"2:"both"3:"  three"] for in somedict {   print (  " dictionary key \ (key)-  dictionary value \ (value)")}

          You can also use the enumerate () method for dictionary traversal, which returns the index of the dictionary and (key, Value) pairs:
               

    import uikitvar somedict:[int:string]  = [1 :  one   ", 2 : "   , 3 :  " three   "   for  (key, value) in   somedict.enumerate () {print ( "   dictionary key \ (key)-dictionary (key, Value) to \ (value)   " /span> 

   · Dictionary conversions to Arrays:
   You can extract the Dictionary's key value (key-value) pair and convert it to a separate array:
   Let Dictkeys = [Int] (somedic.keys)
   Let dictvalues = [String] (somedic.values)
   · Count Property
   · IsEmpty Property

Studying-swift:day02