1. EEC-492/693/793 iPhone Application Development
Lecture 10
Wenbing Zhao & Nigamanth Sridhar
9/21/2018
EEC492/693/793 - iPhone Application Development

2. Outline Objective-C Introduction to table views Assignments:
Categories
Introduction to table views
UITableView and UITableViewCell
Grouped and indexed sections
Creating UI elements in Code
UISearchBar and magnifying glass
Assignments:
Various table view apps (chapter 8)
Continue building the calculator app
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EEC492/693/793 - iPhone Application Development
EEC492/693/793 - iPhone Application Development 2

3. EEC492/693/793 - iPhone Application Development
Category
How to add new behavior to an existing class?
Subclassing
Categories
You can add methods to any existing class
You can even override methods the class inherits
However, you cannot add instance variables to a class
Category method names must be unique across an application
When names collide, the category wins, i.e., your category method will completely replace the original method
The method you added to the class will be accessible to any instance or subclass of the class
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EEC492/693/793 - iPhone Application Development

4. How to Define a Category
Example: adding deep copy to NSDictionary
@interface ClassToAddMethodsTo (category)
...methods go here
@end
#import <Foundation/Foundation.h>
@interface NSDictionary(MutableDeepCopy)
- (NSMutableDictionary *)mutableDeepCopy;
@end
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EEC492/693/793 - iPhone Application Development

5. Implementation and Use a Category
#import "NSDictionary-MutableDeepCopy.h"
@implementation NSDictionary (MutableDeepCopy)
- (NSMutableDictionary *) mutableDeepCopy {
NSMutableDictionary *ret = [[NSMutableDictionary alloc]
initWithCapacity:[self count]];
NSArray *keys = [self allKeys];
for (id key in keys) {
id oneValue = [self valueForKey:key]; id oneCopy = nil;
if ([oneValue
oneCopy = [oneValue mutableDeepCopy];
else if ([oneValue
oneCopy = [oneValue mutableCopy];
if (oneCopy == nil)
oneCopy = [oneValue copy];
[ret setValue:oneCopy forKey:key]; }
return ret;
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EEC492/693/793 - iPhone Application Development

6. EEC492/693/793 - iPhone Application Development
Fast Enumeration
for (id key in keys) // fast enumeration
It allows you to quickly iterate through a collection, such as NSArray, without the hassle of creating additional objects or loop variables
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EEC492/693/793 - iPhone Application Development

7. Other Uses of Categories
Splitting an implementation into multiple .m files. For example:
@interface NSWindow : NSResponder
@interface NSWindow(NSKeyboardUI)
@interface NSWindow(NSToolbarSupport)
@interface NSWindow(NSDrag)
@interface NSWindow(NSCarbonExtensions)
@interface NSObject(NSWindowDelegate)
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EEC492/693/793 - iPhone Application Development

8. Other Uses of Categories
Making forward references
Objective-C doesn’t have any truly private methods
If you know the method name, you can call it, even if there is no declaration for that method in the
However, doing so you would see a compiler warning: ‘AClass’ may not respond to ‘-privateMethod:”
To avoid the warning, you can declare the private method as a category at the top of the implementation file
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EEC492/693/793 - iPhone Application Development

9. EEC492/693/793 - iPhone Application Development
Table Views
Table views are the most common mechanism used to display lists of data to the user
Mail uses table views to show lists of accounts, folders, and messages
Table views are not limited to the display of textual data: YouTube, Settings, iPod apps, etc.
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EEC492/693/793 - iPhone Application Development

10. EEC492/693/793 - iPhone Application Development
Table View Basics
Number of rows: no limit
Number of column: one!
Table view: UITableView
Each row: UITableViewCell
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11. EEC492/693/793 - iPhone Application Development
Table View Basics
Table views
Get their configuration data from an object that conforms to the UITableViewDelegate protocol
Get their row data from an object that conforms to the UITableViewDataSource protocol
… Similar to Pickers!
What can be put in a UITableViewCell?
An image, some text, and an optional accessory icon, by default
How to put even more data in a cell?
Add subviews to UITableViewCell
Subclassing UITableViewCell
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EEC492/693/793 - iPhone Application Development

12. EEC492/693/793 - iPhone Application Development
Table View Cell Styles
Cell styles make use of three different cell elements
Image: if an image is part of the specified style, the image is displayed to the left of the cell’s text
Text label: this is the cell’s primary text
Detail text label: the cell’s secondary text, usually used as an explanatory note or label
Default style
Subtitle style
Style value 1 style
Style value 2 style
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EEC492/693/793 - iPhone Application Development

13. Grouped and Plain Tables
Table views come in two basic styles
Grouped: each group is a set of rows embedded in a rounded rectangle
Plain: default style, with no rounded rectangle
It is referred to as indexed when an index is used
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14. EEC492/693/793 - iPhone Application Development
Sections and Rows
Each division of the table is a section
In a grouped table, each group is a section
In an indexed table, each indexed grouping of data is a section
In a plain table without index, the entire table is one section
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15. Table View Data Source Methods for the Simple Table App
Used by the table to ask how many rows are in a particular section
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section {
return [self.listData count]; }
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EEC492/693/793 - iPhone Application Development

16. Table View Data Source Methods for the Simple Table App
Called by the table view when it needs to draw one of its rows
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *SimpleTableIdentifier
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
SimpleTableIdentifier]; // to reduce overhead
if (cell == nil) {
cell = [[[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:SimpleTableIdentifier] autorelease]; }
NSUInteger row = [indexPath row];
cell.textLabel.text = [listData objectAtIndex:row];
return cell;
If that new row can just reuse one of the
cells that has already rolled off the screen, the system can avoid the overhead associated
with constantly creating and releasing those views
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EEC492/693/793 - iPhone Application Development

17. Table View Delegate Methods for the Simple Table App
Setting the indent level
- (NSInteger)tableView:(UITableView *)tableView
indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
return row; }
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EEC492/693/793 - iPhone Application Development

18. Table View Delegate Methods for the Simple Table App
Method called when a user tapped a row (before the row is selected)
-(NSIndexPath *)tableView:(UITableView *)tableView
willSelectRowAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
if (row == 0) // prevent 1st row being selected
return nil;
return indexPath; }
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EEC492/693/793 - iPhone Application Development

19. Table View Delegate Methods for the Simple Table App
Method called after a row is selected
- (void)tableView:(UITableView *)tableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
NSString *rowValue = [listData objectAtIndex:row]; …
[tableView deselectRowAtIndexPath:indexPath animated:YES]; }
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EEC492/693/793 - iPhone Application Development

20. Table View Delegate Methods for the Simple Table App
Method to specify the height of the table rows
- (CGFloat)tableView:(UITableView *)tableView
heightForRowAtIndexPath:(NSIndexPath *)indexPath {
return 70; }
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21. Adding Subviews to the Table View Cell
Coding UI Elements Directly
CGRect nameLabelRect = CGRectMake(0, 5, 70, 15);
UILabel *nameLabel = [[UILabel alloc] initWithFrame:nameLabelRect];
nameLabel.textAlignment = UITextAlignmentRight;
nameLabel.text
nameLabel.font = [UIFont boldSystemFontOfSize:12];
[cell.contentView addSubview: nameLabel];
[nameLabel release];
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EEC492/693/793 - iPhone Application Development

22. Adding Subviews to the Table View Cell
Accessing UI Element via tag
CGRect nameValueRect = CGRectMake(80, 5, 200, 15);
UILabel *nameValue = [[UILabel alloc] initWithFrame:nameValueRect];
nameValue.tag = kNameValueTag;
[cell.contentView addSubview:nameValue];
[nameValue release];
NSUInteger row = [indexPath row];
NSDictionary *rowData = [self.computers objectAtIndex:row];
UILabel *name = (UILabel *)[cell.contentView viewWithTag:kNameValueTag];
name.text = [rowData
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EEC492/693/793 - iPhone Application Development

23. Table View Data Source Methods for the Sections App
Get number of sections
(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [keys count]; }
Specify header value for each section
- (NSString *)tableView:(UITableView *)tableView
titleForHeaderInSection:(NSInteger)section {
NSString *key = [keys objectAtIndex:section];
return key; }
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EEC492/693/793 - iPhone Application Development

24. Table View Delegate Methods for the Sections App
To add an index
- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
return keys; }
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EEC492/693/793 - iPhone Application Development

25. EEC492/693/793 - iPhone Application Development
Adding a Search Bar
What’s needed
Creating a mutable copy of the dictionary and the keys as the data source
Adding an outlet for the table, and another one for the search bar
Adding search method, and reset method
Adding search bar delegate methods
Adding ways of displaying/hiding the index
Adding ways of displaying/hiding the search bar
9/21/2018
EEC492/693/793 - iPhone Application Development