IOS stage learning 15th-day notes (NSDictionary and NSMutableDictionary dictionary), iosnsdictionary

IOS stage learning 15th-day notes (NSDictionary and NSMutableDictionary dictionary), iosnsdictionary

Knowledge points of IOS Learning (oc language)

1. OC dictionary

1) dictionary: A container object. elements are stored in the form of key-value pairs. Keys and values are of any type and keys are unique, the value can be repeated.

2) There are two types of dictionaries in OC:

1. unchangeable dictionary: NSDictionary, which cannot be modified after Initialization

2. Variable dictionary: NSMutableDictionary, which can be modified after initialization.

Ii. NSDictionary dictionary operations

1) create a dictionary object using the instantiation method, for example:

1 NSDictionary * dict1 = [[NSDictionary alloc] initWithObjectsAndKeys: @ "one", @ "1", @ "two", @ "2", @ "three ", @ "3", @ "one11", @ "1", @ "two", @ "22", nil]; 2 // note: the previous one is a value) the last one is the key)

2) count can calculate the number of key-values in the dictionary, for example, NSLog (@ "% ld", [dict1 count]);

3) initWithDictionary creates another dictionary object with one dictionary, for example:
1 NSDictionary * dict2 = [[NSDictionary alloc] initWithDictionary: dict1];

4) dictionaryWithObjectsAndKeys:
1 NSDictionary * dict3 = [NSDictionary dictionaryWithObjectsAndKeys: <# (id),... #>, nil];

5) quickly create an object @ {key1: value1, key2: value2,...}. For example:
1 NSDictionary * dict3 =@ {@ "apple": @ "apple", @ "red": @ "red"}; 2 // note: the front is the key) the value is a bit similar to the Json data type.

6) objectForKey is used to obtain the value based on the key, for example:
1 NSString * value = [dict1 objectForKey: @ "2"]; // result: two

7) allKeysForObject extracts all the corresponding keys based on the value (the values can be repeated, and the keys cannot be repeated) for example:
1 NSArray * keys = [dict1 allKeysForObject: @ "two"];

8) allKeys is used to retrieve all keys, for example:
1 NSArray * allKeys = [dict1 allKeys];
9) allValues is used to retrieve all values, for example:
1 NSArray * allValues = [dict1 allValues];

10) NSDictionary Traversal method

1. iterator method:

1 NSEnumerator * enumerator = [dict1 keyEnumerator]; 2 id obj; 3 // [enumerator nextObject]: If a key exists, it is returned. Otherwise, it is nil, automatically points to the next key4 while (obj = [enumerator nextObject]) {5 NSLog (@ "% @ --> % @", obj, [dict1 objectForKey: obj]); 6}

2. Fast traversal:

1  for(id key in dict1){2   NSLog(@"%@*******%@",key,[dict1 objectForKey:key]);3  }

3. NSMutableDictionary dictionary operations

1) NSMutableDictionary inherits from NSDictionary.

2) create an empty dictionary object, for example, 1 NSMutableDictionary * dict1 = [[NSMutableDictionary alloc] init];

3) setObject... ForKey... If the key does not exist, add it. If the key exists, modify it, for example:
1 [dict1 setObject: @ "one" forKey: @ "1"];

4) addEntriesFromDictionary adds all the content of the other dictionary. For example:

1 NSDictionary *subDict=@{@"2":@"two",@"3":@"three",@"1":@"one1",@"4":@"four"};2 [dict1 addEntriesFromDictionary:subDict];

5) removeObjectForKey: delete an element based on the key (both the key and the corresponding value will be deleted). For example:
1 dict1 removeObjectForKey: @ "1"];

6) removeObjectsForKeys is used to delete multiple keys and corresponding values, for example:
1 NSArray * keys = @ [@ "2", @ "3"]; 2 [dict1 removeObjectsForKeys: keys];

7) removeAllObjects:
1 [dict1 removeAllObjects];

8) setDictionary use another dictionary to reset the dictionary content, for example:
1 [dict1 setDictionary: subDict];

Iv. Package and unpackage in OC

1) package the process of converting a value type data to an object type data, for example:

1 // encapsulate int data into an object (packed) 2 NSNumber * intNumber = [[NSNumber alloc] initWithInt: 100]; 3 NSNumber * longNumber = [NSNumber numberWithInteger: 100]; 4 NSNumber * charNumber = [[NSNumber alloc] initWithChar: 'a'];

2) NSNumber: Used to encapsulate data into objects.

3) Unpack a process that converts an object type to a value type, for example:

1 // retrieve the basic data values in the object (unpack) 2 NSLog (@ "% d", [intNumber intValue]); 3 NSLog (@ "% ld ", [longNumber integerValue]); 4 NSLog (@ "% c", [charNumber charValue]);

4) compare is used to compare the data values of two objects.

Instance code:

1 NSComparisonResult cmp = [intNumber compare: longNumber]; 2 // NSNumber can directly display the data value. The description method has been rewritten. 3 if (cmp = NSOrderedAscending) {4 NSLog (@ "% @ <% @", intNumber, longNumber); 5} else if (cmp = NSOrderedDescending) {6 NSLog (@ "% @> % @", intNumber, longNumber); 7} else if (cmp = NSOrderedSame) {8 NSLog (@ "% @ = % @", intNumber, longNumber); 9}

5) NSValue: encapsulate data of the struct and pointer types into objects.

6) encapsulate struct data into objects. Note: you cannot store struct variables in arrays. You need to encapsulate them as NSValue objects.

Instance code:

1 struct mysct 2 {3 int a; 4 int B; 5}; 6 struct mysct s1 = {1, 2}, s2; 7 NSValue * value1 = [[NSValue alloc] initWithBytes: & s1 objCType: @ encode (struct mysct)]; 8 NSLog (@ "% s, % s", @ encode (struct mysct), @ encode (int )); // result: {mysct = ii}, I 9 NSArray * array1 = [[NSArray alloc] initWithObjects: value1, nil]; 10 // Save the object encapsulated by the struct variable to the array 11 NSArray * array1 = [[NSArray alloc] initWithObjects: value1, nil]; 12 NSValue * value2 = [array1 firstObject]; 13 // store the data in value2 to s214 [value2 getValue: & s2]; 15 NSLog (@ "s2: {% d, % d}", s2.a, s2. B ); // result: 1, 2

7) @ encode (aType) returns the representation of this type of C string (char.

5. Random Number Generation in OC

1. rand is used to generate random numbers of the int type. rand () is not a real pseudo-random number generator, and random () is relatively better.

2. random is used to generate a random number of the long type. The seed needs to be set during initialization, for example:
1 srandom (unsigned int) time (time_t *) NULL); // set the seed during initialization.

3. arc4random is used to generate random data of the unsigned int type, for example:

1 int value = arc4random () % x; // returns an integer random number between 0 and X-1 2 int value = (arc4random () % x) + 1; // returns an integer random number between 1 and x.

6. Structures commonly used in OC

 

1) structures commonly used in OC: NSPoint, NSRect, NSSize, and nsange

1. NSPoint is used to get/set the coordinate point instance code of the object:

1 NSPoint pt = NSMakePoint (10, 20); 2 NSValue * vl1 = [NSValue valueWithPoint: pt]; 3 NSPoint pt2 = [vl1 pointValue]; 4 NSLog (@ "Point = (%. 0f, %. 0f) ", pt2.x, pt2.y); // result: Point = (10, 20)

2. NSRect is used to obtain/set the coordinate point and length and width of an object. The example code is as follows:

1 NSRect rt = NSMakeRect (2, 6, 20, 10); 2 NSValue * vl3 = [NSValue valueWithRect: rt]; 3 NSRect pt4 = [vl3 rectValue]; 4 NSLog (@ "Rect = (%. 0f, %. 0f, %. 0f, %. 0f) ", pt4.origin. x, pt4.origin. y, pt4.size. width, pt4.size. height); // result: Rect = (2, 6, 20, 10)

3. NSSize is used to get/set the object length and width. Example code:

1 NSSize rs=NSMakeSize(30, 60);2 NSValue *vl4=[NSValue valueWithSize:rs];3 NSSize pt5=[vl4 sizeValue];4 NSLog(@"Size=(%.0f,%.0f)",pt5.width,pt5.height);

4. The nsange instance code is used to obtain/set the start coordinate and length of an object:

1 NSRange rg=NSMakeRange(3, 6);2 NSValue *vl2=[NSValue valueWithRange:rg];3 NSRange pt3=[vl2 rangeValue];4 NSLog(@"Range=(%lu,%lu)",pt3.location,pt3.length);

2) The elements in basic data can be operated only when the data is converted to an object.