Cocoa-Matic

SQLite import from .csv file

2012-01-12T13:04:00.001-05:00

Here are the quick and easy steps to import the contents of a .csv file into your SQLite3 database.

Open the db via the command line:

sqlite3 myDatabaseName

Enter the following commands:

.separator ","
.import myFile.csv tblMyTable

And that's it. If your .csv file has a different separator character, just replace the comma with your character.

XCode Linker error: Symbol(s) not found

2011-01-26T17:28:00.000-05:00

Came across a weird error today:

Objc-class-ref-to-[ClassName] in MainController.o
Symbol(s) not found
Collect2: Id returned 1 exit status

For some reason the reference to the class in question is not listed under Compile Sources. Thankfully, it's an easy fix.

1. Under Groups & Files, expand Targets
2. Expand the compile target
3. Expand Compile Sources (xx)
4. Check to see if all of your .m files are listed. If not, drag the missing files in.
5. Recompile and run.

So, not sure why this happens, but luckily there's an easy fix.

UITextField horizontal and vertical alignment

2011-01-26T15:24:00.000-05:00

Horizontal alignment in a UITextField was quick and easy to find:

myTextField.textAlignment = UITextAlignmentLeft;
myTextField.textAlignment = UITextAlignmentCenter;
myTextField.textAlignment = UITextAlignmentRight;

Vertical alignment in a UITextField is equally as easy, just a little harder to find:

myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentTop;
myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentBottom;
myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentFill;

Enjoy!

Replace UINavigationBar background with image

2011-01-12T17:04:00.003-05:00

Sometimes you want to show off some creativity in your apps. One of the easiest ways to do that is by changing the look of the UINavigationBar. Modifying the color is one way and is a trivial task in Interface Builder. What about replacing it entirely with an image? Turns out that's not too difficult either. Here's how...

We're going to use Categories. What are Categories?
From CocoaDevCentral.com: Categories are one of the most useful features of Objective-C. Essentially, a category allows you to add methods to an existing class without subclassing it or needing to know any of the details of how it's implemented.

This is particularly useful because you can add methods to built-in objects. If you want to add a method to all instances of NSString in your application, you just add a category. There's no need to get everything to use a custom subclass.

Step 1

Create a new "Objective-C class" file. I named mine: UINavigationBar-Utility.

Step 2

The header (.h) file should read as follows:

@interface UINavigationBar (Utility)

- (void)drawRect:(CGRect)rect;

@end

*The word "Utility" in parentheses can be any word you choose.

Step 3

The class (.m) file should read as follows:

@implementation UINavigationBar (Utility)

- (void)drawRect:(CGRect)rect {
     UIImage *imgPortrait = [UIImage imageNamed: @"navbar768_1.png"];
     UIImage *imgLandscape = [UIImage imageNamed: @"navbar1024_1.png"]; 
     if (imgPortrait != NULL && imgLandscape != NULL) {
          if(self.frame.size.width == 1024) {
               [imgLandscape drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
          } else {
               [imgPortrait drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
          }
     } else {
          // Draw UINavigation bar yourself
          CGContextRef context = UIGraphicsGetCurrentContext();
          UIColor *color = [UIColor blueColor];
          CGContextSetFillColor(context, CGColorGetComponents([color CGColor]));
          CGContextFillRect(context, rect);
          self.tintColor = color;
     }
}
@end

Basically, we override UINavigationBar's drawRect function. The first part attempts to set a background image, if available. (It also provides a separate image for portrait and landscape modes, which is what the nested if/else accomplishes.) If the images don't exist, we provide the else to simply color the bar blue.

So, there it is. Pretty simple to add some interesting customization to your app.

NSDate number of days between two dates

2010-09-01T17:05:00.001-04:00

Date objects in programming are typically both extremely common and notoriously tricky due to the many different syntaxes involved. These rules apply to iPhone development. In one application I created, I needed the number of days between 2 dates in several instances. As there is no simple NSDate2 - NSDate1 function built-in to return the number of days apart, I wrote a function to accomplish the task. Here it is...

- (int)daysBetweenDates:(NSDate *)dt1:(NSDate *)dt2 {
 int numDays;
 NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
 NSUInteger unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;
 NSDateComponents *components = [gregorian components:unitFlags fromDate:dt1 toDate:dt2 options:0];
 numDays = [components day];
 [gregorian release];
 return numDays;
}

Line 3: I first get a reference to the calendar. (The date objects don't mean much with a calendar reference.)

Line 4: I set the flags of the date parts that I care about for this task. (Note, in this case I don't use NSMonthCalendarUnit, but show it as an example of how to declare multiple flags.)

Line 5: This does the work of determining how many units (days, months, whatever is chosen on Line 4) separate the two dates.

Line 6: Get the component I'm looking for--days in this case.

Hope you'll find this to be a useful addition to your Cocoa toolbox.

Create UIPickerView programmatically

2010-08-20T00:47:00.003-04:00

The UIPickerView is one of the input controls in iOS for displaying and selecting a list of data. Most tutorials implement this control in Interface Builder, which is fine, but I like to have more control and do most everything in code. There are several components to doing this 100% programmatically, which I will demonstrate below...

The first thing we have to do is include the UIPickerViewDelegate in the interface of our class .h file.

@interface myViewController : UIViewController<UIPickerViewDelegate>

Next, actually create the UIPickerView by setting the frame, setting the delegate, making the selection highlight visible and adding it to the main view.

UIPickerView *myPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 200, 320, 200)];
myPickerView.delegate = self;
myPickerView.showsSelectionIndicator = YES;
[self.view addSubview:myPickerView];

Finally, we have to implement the delegate methods to control the look and functionality.

- (void)pickerView:(UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent:(NSInteger)component {
    // Handle the selection
}

// tell the picker how many rows are available for a given component
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    NSUInteger numRows = 5;

    return numRows;
}

// tell the picker how many components it will have
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
 return 1;
}

// tell the picker the title for a given component
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    NSString *title;
    title = [@"" stringByAppendingFormat:@"%d",row];

    return title;
}

// tell the picker the width of each row for a given component
- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
 int sectionWidth = 300;

 return sectionWidth;
}

Prevent UITableView from scrolling

2010-08-18T15:23:00.000-04:00

Quick tip:

UITableView elements enable vertical scrolling by default. The following code disables the scroll:

myTableView.scrollEnabled = NO;

Random Number in Cocoa and Objective-c

2010-08-17T11:25:00.002-04:00

Generating a random number is fairly simple using arc4random(). Say you want a random integer between 10 (min) and 1000 (max). Here's how to do it:

int max = 1000;
int min = 10;
int value = (arc4random() % max) + min;

Also, no need to do any seeding with this method.

Unwanted UITableView gray background on iPad

2010-08-13T13:50:00.002-04:00

I came across something weird when developing an iPad app. I have a UITableView that does not encompass the entire screen and I have it set to grouping mode so it has nice looking rounded corners. For some reason when this is displayed, the background of the UITableView is light gray. It seems to be ignoring the backgroundColor property.

So, here's the fix:

Set the backgroundView to nil.

if ([self.tableView respondsToSelector:@selector(backgroundView)]) {
     self.tableView.backgroundView = nil;
}

Note, it's always a good idea to make sure the object responds to the selector, so that's what the check is all about.

Asynchronous data request class

2010-08-13T00:31:00.002-04:00

A very handly class I've built is asyncDataRequest. This provides for an easy way to make and receive calls to web data feeds. All you have to do is include the class reference in your .m file, make the request and create a notification responder to receive and parse that data response.

First, we'll look at asyncDataRequest.h:

@interface asyncDataRequest : NSObject {
 NSMutableData *responseData;
 id delegate;
 NSString *notificationName;
}

@property(nonatomic,retain) NSMutableData *responseData;
@property(nonatomic,assign) id delegate;
@property(nonatomic,retain) NSString *notificationName;

- (void)setDelegate:(id)newDelegate;
- (void)connection:(NSURLConnection *)connection didReceiveResponse: (NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
- (void)connection:(NSURLConnection *)connection didFailWithError: (NSError *)error;
- (void)connectionDidFinishLoading: (NSURLConnection *)connection;

@end

The code for asyncDataRequest.m is:

#import "asyncDataRequest.h"


@implementation asyncDataRequest
@synthesize responseData, delegate, notificationName;
- (id)delegate {
 return delegate;
}

- (void)setDelegate:(id)newDelegate {
 delegate = newDelegate;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse: (NSURLResponse *)response {
 [self.responseData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
 // Process the downloaded chunk of data.
 [self.responseData appendData:data];
 spLog(@"data: %i", [self.responseData length]);
 
}

- (void) connectionDidFinishLoading: (NSURLConnection *)connection {
 spLog(@"finished");
 
 NSString *asyncReturn = [[NSString alloc] initWithData:self.responseData encoding:NSUTF8StringEncoding];
 if(asyncReturn != NULL) {
  spLog(@"asyncReturn: %@", asyncReturn);
  if([asyncReturn isEqualToString:@"FALSE"] || [asyncReturn hasPrefix:@"ERROR"] || asyncReturn == nil || [[asyncReturn stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] hasPrefix:@"<"] && ![[asyncReturn stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] hasPrefix:@"<form"]) {
   NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
   [dict setObject:[NSNumber numberWithBool:YES] forKey:@"isError"];
   [dict setObject:[NSString stringWithString:@""] forKey:@"response"];
   [[NSNotificationCenter defaultCenter] postNotificationName:self.notificationName object:self userInfo:dict];
   [dict release];
  } else {
   NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
   [dict setObject:[NSNumber numberWithBool:NO] forKey:@"isError"];
   [dict setObject:[NSString stringWithString:asyncReturn] forKey:@"response"];
   [[NSNotificationCenter defaultCenter] postNotificationName:self.notificationName object:self userInfo:dict];
   [dict release];
  }
 }
 [asyncReturn release];
 [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
 
 NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil];
 [NSURLCache setSharedURLCache:sharedCache];
 [sharedCache release];
 
}

- (void) connection:(NSURLConnection *)connection didFailWithError: (NSError *)error {
 spLog(@"error");
 [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
 NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
 [dict setObject:[NSNumber numberWithBool:YES] forKey:@"isError"];
 [dict setObject:[NSString stringWithString:@""] forKey:@"response"];
 [[NSNotificationCenter defaultCenter] postNotificationName:self.notificationName object:self userInfo:dict];
 [dict release];
 
}

- (void)dealloc {
 [self.responseData release];
 [self.notificationName release];
 [super dealloc];
}

@end

In order to implement this method:

NSURL *sURL = [[NSURL alloc] initWithString:urlString];
  
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:sURL];
//create delegate instance
asyncDataRequest *adr = [[asyncDataRequest alloc] init];
adr.notificationName = @"ASYNC_RESPONSE_NOTIFICATION";
[adr setDelegate:self];
  
NSURLConnection *connectionADR = [[NSURLConnection alloc] initWithRequest:request delegate:adr];
if(connectionADR) {
 adr.responseData = [[NSMutableData data] retain];
 [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
} else {
 //connection error
 spLog(@"connection error");
}
[connectionADR release];
[adr release];
[sURL release];
[request release];

You'll also need a notification handler (since this asynchronous after all).

// Add the notification observer in viewDidLoad
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(returnFromAsyncNotification:) name:@"ASYNC_RESPONSE_NOTIFICATION" object:nil];

- (void)returnFromAsyncNotification:(NSNotification *)notify {
 id ndict = [notify userInfo];
 BOOL isError = [[ndict objectForKey:@"isError"] boolValue];
 NSString *strResponse = [ndict objectForKey:@"response"];
 spLog(@"strResponse: %@", strResponse);
 if(isError) {
  // Handle connection error
 } else {
  // Do something with returned data string, strResponse
 }
}

And there you have it. Enjoy!

UIButton with custom UIImage

2010-08-12T14:19:00.000-04:00

Most developers want to steer clear of the default buttons provided in Cocoa because they're just not that attractive. The following code shows how to programmatically create an image button and define an action for when the button is pressed.

// Create button and set frame
UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 100, 50)];
// Set button image, in this case "my_image.png"
[myButton setImage:[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"my_image" ofType:@"png"]] forState:UIControlStateNormal];
// Call buttonWasPressed function when button is touched
[myButton addTarget:self action:@selector(buttonWasPressed) forControlEvents:UIControlEventTouchUpInside];
// Add the button to view
[self.view addSubview:myButton];

UILabel dynamic sizing based on string

2010-08-05T12:34:00.002-04:00

Here's how to create a UILabel that dynamically resizes to fit the NSString that is loaded into it:

UILabel *tmpTitleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 20)];
self.titleLabel = tmpTitleLabel;
[tmpTitleLabel release];
self.titleLabel.textColor = [UIColor blackColor];
self.titleLabel.font = [UIFont boldSystemFontOfSize:16];
self.titleLabel.numberOfLines = 0;
self.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
self.titleLabel.text = self.myTitleString;
 
//Calculate the expected size based on the font and linebreak mode of label
CGSize maximumLabelSize = CGSizeMake(300,9999);
CGSize expectedLabelSize = [self.myTitleString sizeWithFont:self.titleLabel.font constrainedToSize:maximumLabelSize lineBreakMode:self.titleLabel.lineBreakMode];
 
//Adjust the label the the new height
CGRect newFrame = self.titleLabel.frame;
newFrame.size.height = expectedLabelSize.height;
self.titleLabel.frame = newFrame;

And here's the explanation of what's going on with this code:

Lines 1-3: Declare your UILabel using initWithFrame. At this point the size doesn't matter so use any frame size.

Lines 4-7: Sets the display properties for the UILabel.

Line 8: Set the string. In this case self.myTitleString is an NSString.

Line 11: Determine the maximum size for your label. In this case, I'm constraining to 300px wide, with an unlimited height.

Line 12: This is what creates the new size based on the string.

Lines 15-17: Sets the newly calculated frame for self.titleLabel.

Better NSLog implementation

2010-08-04T09:07:00.001-04:00

NSLog is an invaluable tool for developers who are looking to debug and/or troubleshoot code. It outputs to the debugger console during the application runtime. Before I show a better way to use the NSLog function, let's go over the basics with an example:

int myInt = 100;
NSLog(@"The value of myInt: %i", myInt);

This will output:
The value of myInt: 100

Depending on what type of value you're trying to print, you'll have to use different Format Specifiers (%i in the previous example). Here's a list of common Format Specifiers:

Specifier	Description
%@	Cocoa object with -description property
%d, %i	Signed integer
%u	Unsigned integer
%f	Double or Float
%p	Pointer
%s	C String
%c	Character
%ll	Long Long
%Lf	Long Double
%llu	Unsigned Long Long
%x	Hexadecimal
%o	Octal

Now for the "Better NSLog" implementation, which I'm defining as spLog (choose any non-keyword, doesn't matter).

#if DEBUG
# define spLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__);
#else
# define spLog(...)
#endif

This little macro takes NSLog a step further, by including the function name (in which the log call resides) and the line number, as well as whatever you were NSLogging in the first place. It is called in the same way NSLog is called. So the only difference from the first example would be:

int myInt = 100;
spLog(@"The value of myInt: %i", myInt);

This output would be:
-[myViewController myFunction:] [Line 56] The value of myInt: 100

So just include the macro in a header file and you're good to go. When you're debugging, the more information you get, the better and this is a quick way to get it.

UITextField: Only allow numeric entry using NSScanner

2010-08-03T12:52:00.001-04:00

Have a UITextField and want to prevent the user from entering anything but numbers (and decimal point)? This quick function utilizing the UITextFieldDelegate will do the trick.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

 NSString *resultingString = [textField.text stringByReplacingCharactersInRange: range withString: string];
 
 // This allows backspace
 if ([resultingString length] == 0) {
  return true;
 }

 double holder;
 NSScanner *scan = [NSScanner scannerWithString: resultingString];
 
 return [scan scanDouble: &holder] && [scan isAtEnd];
}

If you want an integer instead of a double, change line 10 from

double holder;

NSInteger holder;

and change line 13 from

return [scan scanDouble: &holder] && [scan isAtEnd];

return [scan scanInteger: &holder] && [scan isAtEnd];

Remember, in order for this method to be called, you have to reference the delegate class in your header file and set the delegate property of the UITextField to self.

@interface MyViewController : UIViewController<UITextFieldDelegate> { }

self.myTextField.delegate = self;

UIColor macro with hex values

2010-07-30T16:30:00.002-04:00

Cocoa has several colors built into the UIColor class. For example:

[UIColor redColor];
[UIColor darkGrayColor];

This is great, but what if you want one of the thousands of colors not found in the pre-defined list? There's an easy way to do that:

[UIColor colorWithRed:0.5 green:0.5 blue:0.5 alpha:1.0];

Perfect. But what if you just have a list of hex color codes? Wouldn't it be nice if you didn't have to convert each of the color components in the hex code to its corresponding RGB decimal value? Here's where a simple and very useful macro comes into play. Just place the code below in a header file and you're done. (They're identical except that UIColorFromRGB always sets the alpha value to 1.0, whereas UIColorFromRGBWithAlpha allows you to set the alpha value.)

//RGB color macro
#define UIColorFromRGB(rgbValue) [UIColor \
colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 \
green:((float)((rgbValue & 0xFF00) >> 8))/255.0 \
blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]

//RGB color macro with alpha
#define UIColorFromRGBWithAlpha(rgbValue,a) [UIColor \
colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 \
green:((float)((rgbValue & 0xFF00) >> 8))/255.0 \
blue:((float)(rgbValue & 0xFF))/255.0 alpha:a]

Here's how to call the macros:

self.view.backgroundColor = UIColorFromRGB(0xCECECE);
self.view.backgroundColor = UIColorFromRGBWithAlpha(0xCECECE, 0.8);

This is a good one to keep in your toolbox. Hope it's as useful for you as it is for me.

Creating UIViews programmatically

2010-07-30T12:14:00.000-04:00

If you want to create a new UIViewController object without using a Nib file in Interface Builder, you must use the loadView method. It's rather simple, but key to doing things programmatically.

- (void)loadView {
 CGRect viewFrame;
 viewFrame = CGRectMake(0, 0, MASTER_WIDTH, MASTER_HEIGHT);
 self.view = [[[UIView alloc] initWithFrame:viewFrame] autorelease];
}

(Note: MASTER_WIDTH and MASTER_HEIGHT are simply constants defining the width and height of the screen.)

Once your view is created, you are free to implement, as usual, viewDidLoad, viewWillAppear, viewDidAppear, etc.

Add decimal point to number pad

2009-08-13T15:04:00.000-04:00

Add this to viewDidLoad:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardDidShowWeight:) name:UIKeyboardDidShowNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShowWeight:) name:UIKeyboardWillShowNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardDidHideWeight:) name:UIKeyboardDidHideNotification object:nil];

Add these methods:

- (void)addDecimalPoint:(id)sender {

NSLog(@"decimal point pressed");

BOOL allowDecimal = YES;

unichar c;

unichar d = '.';

for(int i=0;i<[todayWeighInTextField.text length];i++) {

c = [todayWeighInTextField.text characterAtIndex:i];

if(c == d) allowDecimal = NO;

}

if(allowDecimal) todayWeighInTextField.text = [todayWeighInTextField.text stringByAppendingString:@"."];

}

- (void)keyboardDidShowWeight:(NSNotification *)note {

[self.keyboardToolbar setHidden:NO];

}

- (void)keyboardWillShowWeight:(NSNotification *)note {

UIWindow *tmpWindow;

UIViewController *mainViewController = self;

UIView *keyboard;

for(int i=0;i<[[[UIApplication sharedApplication] windows] count];i++) {

tmpWindow = [[[UIApplication sharedApplication] windows] objectAtIndex:i];

for(int j=0;j<[tmpWindow.subviews count];j++) {

keyboard = [tmpWindow.subviews objectAtIndex:j];

if([[keyboard description] hasPrefix:@"] == YES) {

UIButton *decimalPointBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

decimalPointBtn.frame = CGRectMake(0, 164, 106, 53);

[decimalPointBtn setImage:[UIImage imageNamed:@"decimalPointNormal.png"] forState:UIControlStateNormal];

[decimalPointBtn setImage:[UIImage imageNamed:@"decimalPointPressed.png"] forState:UIControlStateHighlighted];

[keyboard addSubview:decimalPointBtn];

[decimalPointBtn addTarget:mainViewController action:@selector(addDecimalPoint:) forControlEvents:UIControlEventTouchUpInside];

return;

}

}

}

}

- (void)keyboardDidHideWeight:(NSNotification *)note {

[[NSNotificationCenter defaultCenter] removeObserver:self];

}