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How to convert NSData to NSString and back


NSString* myString;
myString = [[NSString alloc] initWithData:nsdata encoding:NSASCIIStringEncoding];


NSData* nsdata;
nsdata = [myString dataUsingEncoding: NSASCIIStringEncoding];


How to get the class type of an object?

Say you have a class of type “Car” and you need to check if an object you have at runtime is of that type:

if ([myRuntimeObject isKindOfClass:[Car class]]){
//do something....
}


iPhone : How to add a delete button to a UITableView cell

1. Make sure you have a proper UITableView in place and rigged to the data source and delegate.

2. In the delegate class, add the following code :

- (BOOL)tableView:(UITableView *)tableView
canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
return YES;
}

- (void)tableView:(UITableView *)tableView
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath

{
// remove the item from your data
[myItems removeObjectAtIndex:indexPath.row];

// refresh the table view
[tableView reloadData];
}

For all you Jewish Folks: Kotel Notes iPhone App Released!

iPhone Kotel Notes Application

The application, “Kotel Notes”, provides a cool way to send free wishes and prayers, and have them printed and placed (for real) within the Western Wall Stones in Jerusalem.

Use it before an important exam, deal or any other event which requires some spiritual assistance…

iPhone : famous crash – “this class is not key value coding-compliant for the key”…

If you came across this error :

*** Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key myLabel.’

(replace myLabel with any other name you may have used)

In most cases the cause for this error is a renaming of a UI property such as  an IBoutlet in Xcode without updating the binding in Interface Builder. When you come across this thing, do the following:

1. Look for the controller that holds your property (in the case of the sample above : myLabel)
2. Open the controller’s corresponding Nib file in Interface Builder
3. Reconnect your UI control (in the case of the sample : a UILabel) to the new property name.

iPhone : warning: no ‘-renderInContext:’ method found – solution

There is a simple solution to this pesky warning:

1. Add the following to your .h file :
   #import <QuartzCore/QuartzCore.h>

2. You may also need to add  “CoreGraphics.framework” to your project, if its not already there.

iPhone : warning: no ‘-renderinInContext’ method found

If you are trying to do this:

[myView.layer renderInContext:myCtx];


and get the this warning :

warning: no '-renderinInContext' method found

Simply add the following to the top of your .h file:
#import <QuartzCore/QuartzCore.h>

iPhone : Simple method for converting radians to degrees

This is a simple method that you can use to throw degrees in and get radians out.


// put this static method somewhere convenient
+ (float)degreesToRadians:(float)degrees{
return degrees / 57.2958;
}



iPhone : How to rotate an image

Say you have an UIImageView called : myImage, and you want to rotate it by 35 deg around its center point.

This can be achieved like so:


// first we set the rotation axis. (This is relevant for all transformation actions)
myImage.center = CGPointMake(0, 0);
// then we apply the transform. Quartz uses radians, so we need to pass radian value and not degrees.
// check out my next post on converting radians to degrees...
myImage.transform = CGAffineTransformMakeRotation([degreesToRadians:imageRotationFix]);