OC Foundation 5th Lecture) Dictionary class {collection class array, dictionary, fast Traversal array of collections sort}

I didn't finish the thing yesterday, I made up today.

//

Main.m

The fourth day of the four weeks OC Fifth lecture

//

Created by Scjy on 15/11/5.

Copyright (c) The fourth week of 2015. All rights reserved.

//

Fourth of OC, Third day of week four

Dictionary class {Collection class array, dictionary, collection Fast Traversal array sort}

#import <Foundation/Foundation.h>

int main (int argc,constchar * argv[]) {

@autoreleasepool {

Insert code here ...

NSLog (@ "Hello, world!");

Dictionary class

/*

Dictionaries are used to hold data collections with mapping relationships (Key-value)

For name: John, name is key,key corresponding value is John

A key-value combination is considered an entry, and the dictionary is stored key-value to the container

The characteristics of the dictionary class:

Unlike arrays, dictionaries rely on key access elements (arrays are accessed by subscript)

Key cannot be duplicated, value must be object (if not object with Nsnumber,nsvalue)

Key-value pairs are stored unordered in the dictionary

Dictionaries are also divided into variable dictionaries and immutable dictionaries

Immutable dictionary: Once the dictionary is created, the key value cannot be changed, cannot be added, cannot be deleted, can only read key or value

Variable dictionaries: After the dictionary is created, the key values can be changed, can be added, can be deleted, or read key or value

The elements in the dictionary appear in pairs and cannot appear in a single number (key-value pairs with key values are a pair)

Eat, sleep, play keyboard.

*/

Create a dictionary Nsdictionary

Nsdictionary *dic = [[Nsdictionary Alloc]initwithobjectsandkeys:

@ "BenZ", @ "Car1",

@ "Zhang", @ "Car2",

@ "Eat", @ "Car3",

@ "Sleep", @ "CAR4",

@ "beat Peas", @ "CAR5",

@ "Actually is playing keyboard", @ "CAR6", nil];

Get the number of dictionary elements

Nsuinteger count = Dic.count;

NSLog (@ "count =%lu", count);

//

Get all key values

Nsarray *allkeyarray = Dic.allkeys;

//

for (int i = 0; i<allkeyarray.count; i++) {

NSLog (@ "allkeyarray[%d] =%@", I,[allkeyarray objectatindex:i]);

//        }

NSLog (@ "%@", [dic AllKeys]);

//

//

Get all value values

Nsarray *allvaluesarray = dic.allvalues;

//

for (int i = 0; i<allvaluesarray.count; i++) {

NSLog (@ "allvaluesarray[%d] =%@", I,[allvaluesarray objectatindex:i]);

//        }

NSLog (@ "%@", [dic allvalues]);

//

//

Query value value by key

NSString *car1 = [dic valueforkey:@ "Car1"];

NSLog (@ "car =%@", car1);

//

NSString *car2 = [dic valueforkey:@ "Car2"];

NSLog (@ "car =%@", car2);

//

Variable dictionaries

Initialization method

Nsmutabledictionary *mdictionary = [[Nsmutabledictionary Alloc]initwithobjectsandkeys:

@ "BenZ", @ "Car1",

@ "Zhang", @ "Car2",

@ "Eat", @ "Car3",

@ "Sleep", @ "CAR4",

@ "beat Peas", @ "CAR5",

@ "Actually is playing keyboard", @ "CAR6", nil];

Initializes a new variable dictionary using an existing immutable dictionary

Nsmutabledictionary *mdic1 = [[Nsmutabledictionary alloc]initwithdictionary:dic];

//

To create a new, empty variable dictionary using the Convenience builder method

Nsmutabledictionary *mdic2 = [Nsmutabledictionary dictionary];

//

Delete and change

Add a key value pair

Gaolen is key, tease is value

[Mdictionary setobject:@ "Doubi" forkey:@ "Gaoleng"];

NSLog (@ "%@", mdictionary);

Modify value for key

[Mdictionary setobject:@ "Shifou" forkeyedsubscript:@ "car2"];

NSLog (@ "%@", mdictionary);

//

[Mdictionary setobject:@ "Shifou" forkeyedsubscript:@ "CAR7"];

NSLog (@ "%@", mdictionary);

//

Setvalue:forvalue: When to add a key value pair, when to modify the key value pairs.

When this key is not in the dictionary, Setvalue:forvalue: Just add a new key value pair

When the dictionary has this key, Setvalue:forvalue: is to modify the current key corresponding to the value

//

//

Delete key value pairs

[Mdictionary removeobjectforkey:@ "Car3"];

NSLog (@ "%@", mdictionary);

Traversal key value pairs

Nsarray *array10=[mdictionary AllKeys];

for (int i=0; i<array10.count; i++) {

NSLog (@ "%@%@", [Mdictionary Valueforkey:array10[i]], array10[i]);

//        }

Traversal key-value pairs method 2