OC Learning Notes Foundation Collection Class Dictionary dictionary

A dictionary of data sets consisting of key-value pairs

4 Ways to create dictionaries

1> direct assignment for a single key-value pair

 1Nsdictionary *dic = [Nsdictionary dictionarywithobject:@"Dajie"Forkey:@"name"];//Create a dictionary directly 2     ID Object= [dic Objectforkey:@"name"];//remove the name key corresponding value 3NSLog (@"%@",Object);

2> creation of a collection with key values

1Nsarray *obj = @[@"Dajie",@"ly"];2Nsarray *keys = @[@"name",@"Address"];3Nsdictionary *dic1 =[Nsdictionary dictionarywithobjects:obj Forkeys:keys]; //Create a dictionary 4NSLog (@"%@", Dic1);

3> Create and assign values directly

1      Nsdictionary *dic2 = [nsdictionary dictionarywithobjectsandkeys:@ "Dajie",@ " name ",@" ly"@"address", Nil];//nil not less  2      NSLog (@ "\ n---%@", Dic2);

3      id obj2 = [dic2 objectforkey:@ "name"];//based on key to remove corresponding value 4      NSLog (@ "%@", obj2); 

Commonly used in 4> development

//Xcode is commonly used in the development of new features theNsdictionary *dic3 = @{@"name":@"Dajie",@"Address":@"ly",@"QQ":@"12324124"}; -NSLog (@"%@\n--%@--%ld", DIC3,[DIC3 Objectforkey:@"name"],dic3.count);

Variable dictionaries

2      Nsmutabledictionary *mdic = [Nsmutabledictionary dictionary];//created

Adding elements and deleting elements

//to add a key-value pair -[MDic setobject:@"Dajie"Forkey:@" Person"]; +[MDic setobject:@"Hashiqi"Forkey:@"Dog"]; A[MDic setobject:@"Shapi"Forkey:@"Dog"];//The primary key is the same as the dictionary element, which is overwritten atNSString *str = mdic[@"Dog"]; -NSLog (@"%@", str); -   //Delete -[MDic removeallobjects]; -[MDic Removeobjectforkey:@"Dog"]; -NSLog (@"%@", MDic);

Traversing elements

1 Basic for Loop traversal

Nsdictionary *newdic = @{ to                              @"name":@"Dajie", +                              @"Dog":@"Hashiqi"
}; -Nsarray *key = [Newdic AllKeys];//Take out all the keys the      for(intI i < Newdic.count; i++) { *NSString *keys =Key[i]; $NSString *value =Newdic[keys];Panax NotoginsengNSLog (@"%@ = %@", keys,value); -}

2 Simple traversal

// It is recommended to use fast traversal  +     enumeratekeysandobjectsusingblock: ^ (ID-IDBOOL *stop) {         NSLog (@ "", key, obj);      ];

OC Learning Notes Foundation Collection Class Dictionary dictionary