IOS dictionary NSDictionary and NSMutableDictionary knowledge points, iosnsdictionary

IOS dictionary NSDictionary and NSMutableDictionary knowledge points, iosnsdictionary

 

The elements in the dictionary are stored in the form of key-value pairs. The keys and values of key-value pairs are all arbitrary objects, but keys often use strings. The address of the objects stored in the dictionary is not sequential, dictionary traversal is divided into: the traversal of keys and values, the difference between the dictionary and the array: the array pays attention to order, and the dictionary can help us quickly find data, data is our purpose, the key is our method. NSMutableDictionary is a subclass of NSDictionary, so it has all the functions of NSDictionary. It mainly involves some common operations. For other operations, see the relevant documentation, the following code also uses a third-party plug-in BlocksKit;

A: NSDictionary is a data set composed of key-value pairs.
B: Key: It can be any object (typically an NSString type object), and the key must be a single value.
C: Value: It can be any object and cannot be nil
D: common method: we can find the corresponding value based on the key.
E: The dictionary can be changeable or immutable. The dictionary can dynamically add or delete elements.
F: Unlike arrays, the dictionary is unordered.

1: Some Common NSDictionary operations

 

// Create a dictionary NSDictionary * dictionary = [NSDictionary dictionaryWithObjectsAndKeys: @ "wujy", @ "name", @ 29, @ "age", nil]; NSInteger Count = [dictionary count]; NSLog (@ "the number of dictionaries is % ld", Count); // obtain all keys in the dictionary NSEnumerator * enumeratorkey = [dictionary keyEnumerator]; for (NSObject * obj in enumeratorkey) {NSLog (@ "key: % @", obj); NSLog (@ "value found through key: % @", [dictionary objectForKey: obj]);} // obtain all value values in the dictionary NSEnumerator * enumeratorvalue = [dictionary objectEnumerator]; for (NSObject * obj in enumeratorvalue) {NSLog (@ "value: % @", obj);} // you can easily create NSDictionary * newDictionary = @ {@ "name" after the value column of the key column ": @ "wujy", @ "age": @ 29}; NSArray * keyArray = [newDictionary allKeys]; for (NSObject * obj in keyArray) {NSLog (@ "key value: % @", obj);} NSArray * valueArray = [newDictionary allValues]; for (NSObject * obj in valueArray) {NSLog (@ "value: % @", obj);} // blocks dicnsdictionary * blockDictionary = [NSDictionary dictionaryWithObjects: [[NSArray alloc] initWithObjects: @ 3, @ 15, @ 29, nil] forKeys: [[NSArray alloc] initWithObjects: @ "IOS", @ "work", @ "age", nil]; // traverse [blockDictionary bk_each: ^ (id key, id obj) {NSLog (@ "the key for using blocks is: % @", key ); NSLog (@ "corresponding value: % @", obj) ;}]; // The filter is stopped only when the first one meets the condition.

NSDictionary * matchDictionary = [blockDictionary bk_match: ^ BOOL (id key, id obj ){

BOOL select = [obj intValue] <10? YES: NO; return select;}]; NSLog (@ "match matches: % @", matchDictionary); // filter NSDictionary * selectDictionary = [blockDictionary bk_select: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 10? YES: NO; return select;}]; NSLog (@ "select matches % @", selectDictionary); // Reverse filter NSDictionary * rejectDictionary = [blockDictionary bk_reject: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 10? YES: NO; return select;}]; NSLog (@ "reject matches % @", rejectDictionary ); // modify each item NSDictionary * mapDictinary = [blockDictionary bk_map: ^ id (id key, id obj) {return [NSNumber numberWithInt: [obj intValue] + 1];}]; NSLog (@ "the modified map item is % @", mapDictinary ); // if the condition is met, return bool BOOL isSelected = [blockDictionary bk_any: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 20? YES: NO; return select;}]; NSLog (@ "% d meets the condition", isSelected ); // determine if all items meet this condition BOOL allSelected = [blockDictionary bk_all: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 20? YES: NO; return select;}]; NSLog (@ "% d meets the condition", allSelected ); // determine if all items do not meet this condition BOOL noneSelected = [blockDictionary bk_none: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 50? YES: NO; return select;}]; NSLog (@ "% d meets the condition", noneSelected );

 

2: Some Common NSMutableDictionary operations

// Create an optional nsmutabledictionary * mutableDictionary = [NSMutableDictionary dictionary failed: 3]; [mutableDictionary setObject: @ "wujy" forKey: @ "name"]; [mutableDictionary setObject: @ "cnblogs.com/wujy" forKey: @ "webName"]; [mutableDictionary setObject: @ 29 forKey: @ "age"]; // obtain all keys in the dictionary NSEnumerator * enumeratorkey = [mutableDictionary keyEnumerator]; for (NSObject * obj in enumeratorkey ){ NSLog (@ "key: % @", obj); NSLog (@ "the value of value found through key is: % @", [mutableDictionary objectForKey: obj]);} // delete one of the keys [mutableDictionary removeObjectForKey: @ "name"]; NSLog (@ "Delete the key after name: % @", mutableDictionary); [mutableDictionary removeAllObjects]; NSLog (@ "after deleting all, the number of variable dictionaries is % ld", [mutableDictionary count]); // blocks // filter NSMutableDictionary * newmutableDictionary = [NSMutableDictionary dictionaryWithDictionary: @ {@ "IOS": @ 3, @ "work": @ 13, @ "age": @ 29}]; [newmutableDictionary bk_performSelect: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 10? YES: NO; return select;}]; NSLog (@ "the filtered variable dictionary is () % @", newmutableDictionary); // obtain the anti-filter [newmutableDictionary bk_1_mreject: ^ BOOL (id key, id obj) {BOOL select = [obj intValue]> 20? YES: NO; return select;}]; NSLog (@ "the variable dictionary for anti-filtering is (13) % @", newmutableDictionary ); // modify the results of each item [newmutableDictionary bk_performMap: ^ id (id key, id obj) {return @ ([obj intValue] + 1);}]; NSLog (@ "the modified variable dictionary is (14) % @", newmutableDictionary );