OC learning --- NSDirctionary class and NSMutableDirctionary class in the Foundation framework, nsmutablearray

OC learning --- NSDirctionary class and NSMutableDirctionary class in the Foundation framework, nsmutablearray

I learned about NSArray and NSMutableArray classes in the Foundation framework yesterday.

I. NSDirctionary class

//// Main. m // 19_NSDictionary /// Created by jiangwei on 14-10-12. // Copyright (c) 2014 jiangwei. all rights reserved. // # import <Foundation/Foundation. h> // a data set consisting of key-value pairs, int main (int argc, const char * argv []) {@ autoreleasepool {// 1. create NSArray * array1 = [NSArray arrayWithObjects: @ "zhangsan", @ "zhangfei", nil]; NSArray * array2 = [NSArray arrayWithObjects: @ "lisi ", @ "liping", nil]; // The first element: key: @ "zhang" value: array1 // The second element: key: @ "li" value: array2 NSDictionary * dict = [[NSDictionary alloc] initWithObjectsAndKeys: array1, @ "zhang", array2, @ "li", nil]; NSLog (@ "% @", dict ); // store an element NSDictionary * dict2 = [NSDictionary dictionaryWithObject: array1 forKey: @ "zhang"]; // 2. --------------------- obtain all key NSArray * allKeys = [dict allKeys]; // 3. --------------------- obtain all values // it may be a two-dimensional array NSArray * allValues = [dict allValues]; // 4. --------------------- obtain value NSArray * values = [dict objectForKey: @ "zhang"] through key; // 5. --------------------- optimized syntax NSDictionary * dict3 =@ {@ "zhangsan": array1, @ "lisi": array2}; NSLog (@ "% @", dict3 ); NSArray * array4 = dict3 [@ "zhang"];} return 0 ;}

1. Creation Method

// 1. create NSArray * array1 = [NSArray arrayWithObjects: @ "zhangsan", @ "zhangfei", nil]; NSArray * array2 = [NSArray arrayWithObjects: @ "lisi ", @ "liping", nil]; // The first element: key: @ "zhang" value: array1 // The second element: key: @ "li" value: array2NSDictionary * dict = [[NSDictionary alloc] initWithObjectsAndKeys: array1, @ "zhang", array2, @ "li", nil]; NSLog (@ "% @", dict );

We can see that the NSDirctionary class is created based on NSArray, and the rest is similar to the Map in Java, which is generally in the key-value format. Of course, here we also need to note that the end is: nil

Running result:

The printed result is a key-value style.

2. Add Elements

// Store an element NSDictionary * dict2 = [NSDictionary dictionaryWithObject: array1 forKey: @ "zhang"];

3. Get the key of all elements

// 2. --------------------- obtain all keyNSArray * allKeys = [dict allKeys];

4. Obtain the value of all elements

// 3. --------------------- obtain all values // it may be a two-dimensional array NSArray * allValues = [dict allValues];

5. Get value through key

// 4. --------------------- obtain valueNSArray * values = [dict objectForKey: @ "zhang"] through the key;

6. Fast creation and access modes of NSDirctionary

// 5. --------------------- optimized syntax NSDictionary * dict3 =@ {@ "zhangsan": array1, @ "lisi": array2}; NSLog (@ "% @", dict3 ); NSArray * array4 = dict3 [@ "zhang"];

Ii. NSMutableDirctionary class

//// Main. m // 20_NSMutableDictionary // Created by jiangwei on 14-10-12. // Copyright (c) 2014 jiangwei. all rights reserved. // # import <Foundation/Foundation. h> // variable dictionary int main (int argc, const char * argv []) {@ autoreleasepool {// 1. ------------- create a variable dictionary with a size of 3 NSMutableDictionary * md1 = [[NSMutableDictionary alloc] centers: 3]; NSArray * array1 = [[NSArray alloc] centers: @ "zhangsan ", @ "lis", nil]; // 2. ------------- Add the element [md1 setObject: array1 forKey: @ "zhang"]; NSMutableDictionary * md2 = [[NSMutableDictionary alloc] initWithCapacity: 3]; [md2 priority: md1]; // 3. ------------- delete an element [md1 removeObjectForKey: @ "zhang"]; // Delete [md1 removeAllObjects] with a key; // delete all elements [md1 removeObjectsForKeys: array1]; // Delete with value // 4. ------------- looping dictionary // fast traversing for (NSString * key in md1) {NSArray * values = [md1 objectForKey: key]; for (NSString * v in values) {NSLog (@ "% @", v) ;}// normal traversal NSArray * allKey = [md1 allKeys]; for (int I = 0; I <allKey. count; I ++) {NSArray * value = [md1 objectForKey: allKey [I];} // The dictionary is unordered} return 0 ;}

The previous NSDirctionary class is an unchangeable dictionary, and the same OC also has the corresponding variable dictionary: NSMutableDirctionary

1. Create a variable dictionary

// 1. ------------- create a variable dictionary with a size of 3 NSMutableDictionary * md1 = [[NSMutableDictionary alloc] centers: 3]; NSArray * array1 = [[NSArray alloc] centers: @ "zhangsan ", @ "lis", nil];

Create a variable dictionary and specify its size. Of course, when the capacity is full, it automatically scales back.

2. Add Elements

// 2. ------------- Add the element [md1 setObject: array1 forKey: @ "zhang"]; NSMutableDictionary * md2 = [[NSMutableDictionary alloc] initWithCapacity: 3]; [md2 priority: md1];

3. Delete Elements

// 3. ------------- delete an element [md1 removeObjectForKey: @ "zhang"]; // Delete [md1 removeAllObjects] with a key; // delete all elements [md1 removeObjectsForKeys: array1]; // Delete the element with a value

4. traverse the dictionary

// 4. ------------- looping dictionary // fast traversing for (NSString * key in md1) {NSArray * values = [md1 objectForKey: key]; for (NSString * v in values) {NSLog (@ "% @", v) ;}// normal traversal NSArray * allKey = [md1 allKeys]; for (int I = 0; I <allKey. count; I ++) {NSArray * value = [md1 objectForKey: allKey [I];}

Summary

This article introduces the NSDirctionary and NSMutableDirctionary classes in OC. Their usage is very important and often used later.