Knowledge about arrays

[OBJC] View plaincopy

2. To create an empty array

4. Nsarray *array = [Nsarray array];

6. Create an array with 1 elements

8. Array = [Nsarray arraywithobject:@ "123"];

10. To create an array with multiple elements

12. Array = [Nsarray arraywithobjects:@ "a", @ "B", @ "C", nil Nil];

14. Nsarray *array3 = [Array Arraybyaddingobjectsfromarray:[nsarray arraywithobjects:@ "4", @ "5", nil Nil]];

18. Nsarray *array4 = [Nsarray arraywithobjects:@ "1", @ "2", @ "3", @ "4", nil Nil];

20. Nsrange range = Nsmakerange (1, 2);

22. Nsarray *array5 = [Array4 subarraywithrange:range];

2. Some basic methods of arrays

[OBJC] View plaincopy

2. int count = [array count];//number

4. Determine if an element is included

6. if ([Array containsobject:@ "a"]) {

8. NSLog (@ "contains string a");

10. }

12. NSString *last = [array lastobject]; last element

14. NSString *str = [array objectatindex:1]; Gets the elements in the array according to the index

16. int index = [array indexofobject:@ "C"]; Gets the index of the specified element

18. Let all objects inside the array call the test method, 123 is the parameter

20. Nsarray *array = [Nsarray arraywithobjects:stu1, STU2, STU3, nil Nil];

22. [Array makeobjectsperformselector: @selector (test2:) withobject:@ "123"];

24. Nsarray *array = [Nsarray arraywithobjects:@ "1", @ "2", @ "3", @ "4", nil Nil];

26. 1-2-3-4

28. Use separators-to stitch all array elements

30. NSString *str = [Array componentsjoinedbystring:@ "-"];

32. Writes an array to a file (an XML file is generated)

34. NSString *path = @ "/users/apple/desktop/array.xml";

36. [Array Writetofile:path atomically:yes];

38. Path = @ "/users/apple/desktop/array.txt";

40. Reading array contents from a file (file has strict formatting requirements)

42. Nsarray *array2 = [Nsarray Arraywithcontentsoffile:path];

3. Iterating through an array

[OBJC] View plaincopy

2. #pragma mark iterates through the array 1

4. void ArrayFor1 () {

6. Nsarray *array = [Nsarray arraywithobjects:stu1, @ "1", @ "2", @ "3", nil Nil];

8. int count = Array.count;

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

12. ID obj = [array objectatindex:i];

14. }

16. }

20. #pragma mark iterates through the array 2 fast traversal

22. void ArrayFor2 () {

24. Student *STU1 = [Student Student];

26. Nsarray *array = [Nsarray arraywithobjects:stu1, @ "1", @ "2", @ "3", nil Nil];

28. int i = 0;

30. for (ID obj in array) {

32. NSLog (@ "%i-%@", I, obj);

34. i++;

36. }

38. }

42. #pragma mark iterates through the array 3

44. void ArrayFor3 () {

46. Student *STU1 = [Student Student];

48. Nsarray *array = [Nsarray arraywithobjects:stu1, @ "1", @ "2", @ "3", nil Nil];

50. [Array Enumerateobjectsusingblock:

52. ^ (ID obj, Nsuinteger idx, Boolbool *stop) {

54. NSLog (@ "%i-%@", idx, obj);

56. If the index is 1, stop traversing

58. if (idx = = 1) {

60. Using pointers to modify the value of a bool variable outside

62. *stop = YES;

64. }

66. }];

68. }

72. #pragma mark iterates through the array 4

74. void ArrayFor4 () {

76. Student *STU1 = [Student Student];

78. Nsarray *array = [Nsarray arraywithobjects:stu1, @ "1", @ "2", @ "3", nil Nil];

80. Get an iterator to an array

82. Nsenumerator *enumerator = [array objectenumerator];

84. Reverse-order iterator (traversing elements from the tail)

86. Nsenumerator *enumerator = [array reverseobjectenumerator];

88. AllObjects is to remove objects that have not been traversed

90. Nsarray *array2 = [enumerator allobjects];

92. NSLog (@ "array2:%@", array2);

94. Gets the next element to traverse

96. ID obj = nil;

98. while (obj = [Enumerator nextobject]) {

100. NSLog (@ "obj=%@", obj);

102. }

104. }

4. Array sorting

[OBJC] View plaincopy

2. #pragma mark Array Sort 1

4. void ArraySort1 () {

6. Nsarray *array = [Nsarray arraywithobjects:@ "2", @ "3", @ "1", @ "4", nil Nil];

10. Returns an ordered array that does not change the order of the elements in the original array

12. The comparison method for the specified element: compare:

14. Nsarray *array2 = [Array sortedarrayusingselector: @selector (compare:)];

16. NSLog (@ "array2:%@", array2);

18. }

22. #pragma mark Array Sort 2

24. void ArraySort2 () {

26. Student *STU1 = [Student studentwithfirstname:@ "Mingjie" lastname:@ "Li"];

28. Student *STU2 = [Student studentwithfirstname:@ "Longhu" lastname:@ "Huang"];

30. Student *STU3 = [Student studentwithfirstname:@ "Lianjie" lastname:@ "Li"];

32. Student *stu4 = [Student studentwithfirstname:@ "Jian" lastname:@ "Xiao"];

34. Nsarray *array = [Nsarray arraywithobjects:stu1,stu2,stu3, Stu4, nil Nil];

36. Specify a comparison method for sorting

38. Nsarray *array2 = [Array sortedarrayusingselector: @selector (comparestudent:)];

40. NSLog (@ "array2:%@", array2);

42. }

44. -(Nscomparisonresult) Comparestudent: (Student *) Stu {

46. Sort by last name first

48. Nscomparisonresult result = [Self.lastname compare:stu.lastname];

50. If you have the same last name, compare the names.

52. if (result = = Nsorderedsame) {

54. result = [Self.firstname compare:stu.firstname];

56. }

58. return result;

60. }

64. #pragma mark Array Sort 3

66. void ArraySort3 () {

68. Student *STU1 = [Student studentwithfirstname:@ "Mingjie" lastname:@ "Li"];

70. Student *STU2 = [Student studentwithfirstname:@ "Longhu" lastname:@ "Huang"];

72. Student *STU3 = [Student studentwithfirstname:@ "Lianjie" lastname:@ "Li"];

74. Student *stu4 = [Student studentwithfirstname:@ "Jian" lastname:@ "Xiao"];

76. Nsarray *array = [Nsarray arraywithobjects:stu1,stu2,stu3, Stu4, nil Nil];

80. Sort by block

82. Nsarray *array2 = [Array sortedarrayusingcomparator:

84. ^nscomparisonresult (Student *obj1, Student *obj2) {

86. Sort by last name first

88. Nscomparisonresult result = [Obj1.lastname compare:obj2.lastname];

90. If you have the same last name, compare the names.

92. if (result = = Nsorderedsame) {

94. result = [Obj1.firstname compare:obj2.firstname];

96. }

100. return result;

102. }];

106. NSLog (@ "array2:%@", array2);

108. }

112. #pragma mark Array Sort 4-advanced sort

114. void ArraySort4 () {

116. Student *STU1 = [Student studentwithfirstname:@ "Mingjie" lastname:@ "Li" bookname:@ "Book1"];

118. Student *STU2 = [Student studentwithfirstname:@ "Longhu" lastname:@ "Huang" bookname:@ "Book2"];

120. Student *STU3 = [Student studentwithfirstname:@ "Lianjie" lastname:@ "Li" bookname:@ "Book2"];

122. Student *stu4 = [Student studentwithfirstname:@ "Jian" lastname:@ "Xiao" bookname:@ "Book1"];

124. Nsarray *array = [Nsarray arraywithobjects:stu1,stu2,stu3, Stu4, nil Nil];

128. 1. Sort by Title first

130. The key here is the name of @property.

132. Nssortdescriptor *booknamedesc = [Nssortdescriptor sortdescriptorwithkey:@ "Book.name" Ascending:YES];

134. 2. Sort by last Name

136. Nssortdescriptor *lastnamedesc = [Nssortdescriptor sortdescriptorwithkey:@ "LastName" Ascending:yes];

138. 3. Sort by name again

140. Nssortdescriptor *firstnamedesc = [nssortdescriptor sortdescriptorwithkey:@ "FirstName" Ascending:yes];

142. Add a sort descriptor sequentially

144. Nsarray *descs = [Nsarray arraywithobjects:booknamedesc, Lastnamedesc, Firstnamedesc, nil Nil];

148. Nsarray *array2 = [array Sortedarrayusingdescriptors:descs];

152. NSLog (@ "array2:%@", array2);

154. }

Knowledge about arrays