iOS development OC (20)--foundation (5) nsdictionary

/*

Collection

1.nsarray\nsmutablearray

• Orderly

• fast Creation (immutable): @[obj1, Obj2, Obj3]

• Quick access to elements: array name [i]

2.nsset\nsmutableset

• unordered

3.nsdictionary\nsmutabledictionary

• unordered

• fast Creation (immutable): @{key1:value1, key2:value2}

• Quick access to elements: dictionary name [key]

*/

Nsdictionary: Dictionary

code example

1>

voidCreate () {/*dictionary: Key----> Value Index----> The contents stored in the text content are keys .*/    //How dictionaries are created//nsdictionary *dict = [nsdictionary dictionarywithobject:@ "Jack" forkey:@ "name"]; //Nsarray *keys = @[@ "name" @ "Address"]; //Nsarray *objects = @[@ "Jack", @ "Beijing"]; //nsdictionary *dict = [nsdictionary dictionarywithobjects:objects Forkeys:keys];       /*nsdictionary *dict = [nsdictionary Dictionarywithobjectsandkeys: @ "Jack" @ "name" @ "Beijing" @ "address", @ "32423434", @ "QQ", nil];*/        //The most practical wayNsdictionary *dict = @{@"name":@"Jack",@"Address":@"Beijing"}; //id obj = [dict objectforkey:@ "name"]; //Get Value    IDobj = dict[@"name"]; NSLog (@"%@", obj); //returns the number of key-value pairsNSLog (@"%ld", Dict.count);}

2> Basic Use

voiduse1 () {nsmutabledictionary*dict =[Nsmutabledictionary dictionary]; //to add a key-value pair[Dict setobject:@"Jack"Forkey:@"name"]; [Dict setobject:@"Beijing"Forkey:@"Address"]; [Dict setobject:@"Rose"Forkey:@"name"]; //removing key-value pairs//[dict removeobjectforkey:<# (ID) #>];NSString*str = dict[@"name"]; //NSLog (@ "%@", str);NSLog (@"%@", Dict); //NSLog (@ "%@", @[@ "Jack", @ "Rose"]);}voidUse2 () {nsmutabledictionary*dict = @{@"name":@"Jack"}; [Dict setobject:@"Rose"Forkey:@"name"];}voiduse3 () {//The dictionary does not allow the same key, but allows the same value (Object)//The disordered of the dictionaryNsdictionary *dict = @{    @"Address":@"Beijing",    @"name":@"Jack",    @"name2":@"Jack",    @"Name3":@"Jack",    @"QQ":@"7657567765"}; //Nsarray *keys = [Dict AllKeys]; //    //for (int i = 0; i<dict.count; i++)//    {    //nsstring *key = keys[i]; //nsstring *object = Dict[key]; //    //    //NSLog (@ "%@ =%@", key, object); //    }     //use block to access[dict enumeratekeysandobjectsusingblock:^(IDKeyIDobj, BOOL *stop) {NSLog (@"%@ - %@", key, obj); //*stop = YES;     }];}

#import<Foundation/Foundation.h>intMain () {Nsarray*persons = @[    @{@"name":@"Jack",@"QQ":@"432423423",@"Books": @[@"5 minutes of iOS programming",@"5 minutes to break Android programming"]},    @{@"name":@"Rose",@"QQ":@"767567"},    @{@"name":@"Jim",@"QQ":@"423423"},    @{@"name":@"Jake",@"QQ":@"123123213"}    ]; //nsdictionary *jim = persons[2];NSString*bookname = persons[0][@"Books"][1]; NSLog (@"%@", BookName); //Nsarray *array = persons[0][@ "Books"]; //NSLog (@ "%@", array); //Remove the 1-bit dictionary first//and then take out the dictionary of QQ this key corresponding data//NSLog (@ "%@", persons[1][@ "QQ"]); //NSLog (@ "%@", Jim);    return 0;}

The code is in the previous study, according to Li Mingjie teacher's video knock, again, thanked him, Li said very well, recommend everyone to see, he is not the programming, but a thought, let me benefit.

iOS development OC (20)--foundation (5) nsdictionary