OBJECTIVE-C Foundation Framework Practice--nsdictionary (i) __foundation

A dictionary is a special type of OC, and its function is very powerful. is an important part of foundation. Let's Learn:

#import <Foundation/Foundation.h> int main (int argc, const char * argv[]) {@autoreleasepool {//INSERT Co De here .../* Dictionary: 1. Memory is not contiguous; 2. Use key and value to correspond (key value); 3.KVC: Key-value code;//Create Party
    Type 1; nsdictionary *dict = [nsdictionary dictionarywithobject:@ "1" forkey:@ "a"];
    
    NSLog (@ "%@", dict);
    Create way 2:nsarray *arrvalue = [[Nsarray alloc] initwithobjects:@ "1", @ "2", @ "3", @ "4", nil];
    Nsarray *arrkeys = [[Nsarray alloc] initwithobjects:@ "a", @ "B", @ "C", @ "D", nil];
    Nsdictionary *dict1 = [nsdictionary dictionarywithobjects:arrvalue Forkeys:arrkeys];
    
   
    
    NSLog (@ "%@", Dict1);
    Create Way 3: Simple to create a way;//@{}; a dictionary;!!!!!
    Nsdictionary *dict3 = @{@ "1": @ "a", @ "2": @ "B"};
    
    
    NSLog (@ "%@", dict3);
    Length: int count = (int) dict3.count;
    
    
    
    NSLog (@ "Count =%d", count);
    Gets the value according to the key nsstring *str = [Dict3 objectforkey:@ "2"];
    NSLog (@ "Key value =%@", str); You can also use the following method: NSString *str2 = [Dict3 valueforkey:@ "2"];
    
    
    NSLog (@ "Key value =%@", str2);
    Gets all the values in the dictionary; (value) Nsarray *ARR5 = [[Nsarray alloc] initwithobjects:@ "1", @ "2", @ "3", nil];
    Nsarray *arrallvalue = [Dict3 objectsforkeys:arr5 notfoundmarker:@ "None"];
    
    NSLog (@ "All values Method 1 =%@", arrallvalue);
    There is also a way to get all the values; Nsarray *arrallvalue2 = [Dict3 allvalues];
    
    
    NSLog (@ "All values Method 2 =%@", arrAllValue2);
    Gets all the keys in the dictionary; (key) Nsarray *arrallkey = [Dict3 AllKeys];
    
    
    NSLog (@ "All keys =%@", Arrallkey);
      Traversal array;//need to use key to traverse; for (NSString *key in dict3) {nsstring *value = [Dict3 Objectforkey:key];
      
    NSLog (@ "key =%@,value =%@", key,value);
    ///using iterators for traversal; nsenumerator *en = [Dict3 keyenumerator];
    ID key = nil;
      while (key = [en nextobject]) {nsstring *str = [Dict3 Objectforkey:key];
      
    NSLog (@ "iterator gets value =%@", str);
} return 0; }

The output results are as follows:

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