Neil Ang

Using EventKit in iOS

2011-09-28T00:00:00-07:00

I presented a talk at /dev/world/2011 on using EventKit and EventKitUI in iOS 4. Below is a summary of the talk, the slides and links to the sample code I used.

What's EventKit?

It is a framework provided by Apple in iOS 4+ for integrating your iOS app with the built in calendar app (iCal). You are able to retrieve events from the calendar, as well as create, update and delete events.

The Simulator

Although there is no calendar application in the iOS simulator, you can still use it for EventKit development. For my talk, I created an application that could retrieve events stored in the simulator, and insert sample ones if the calendar was empty. The code for this sample application is available on github.

Fetching Events

Retrieving stored events from a users calendar is super simple. The only parameters you need to specify is a date range and the calendar you want to query.

EKEventStore *eventStore = [[EKEventStore alloc] init];

NSDate *startDate = [NSDate date];
NSDate *endDate   = [NSDate distantFuture];

NSPredicate *predicate = [eventStore predicateForEventsWithStartDate:startDate
                                                             endDate:endDate
                                                           calendars:nil];
                                                           
NSArray *events = [eventStore eventsMatchingPredicate:predicate];

Calendars within the Calendar app

The calendar app is made up of many calendars, e.g. Home calendar, Work calendar, Birthday calendar etc. Every event created must belong to a calendar, however some calendars are read-only.

You can retrieve the following calendar information in iOS 4:

EKEventStore *eventStore = [[EKEventStore alloc] init];

// Get all calendars
NSArray * calendars = [eventStore calendars];

// Get the default calendar
EKCalendar * calendar = [eventStore defaultCalendarForNewEvents];

// Test if calendar is read-‐only
[calendar allowsContentModifications];

// Get the associated colour of a calendar
[UIColor colorWithCGColor:calendar.CGColor];

Inserting Events

As the following code illustrates, inserting an event to a users calendar is also fairly simple.

EKEventStore *eventStore = [[EKEventStore alloc] init];

EKEvent *event  = [EKEvent eventWithEventStore:eventStore];
event.calendar  = [eventStore defaultCalendarForNewEvents];
event.title     = @"/dev/world/2011";
event.location  = @"Melbourne";
event.notes     = @"AUC Developer Conference";
event.startDate = startDate;
event.endDate   = endDate;
event.allDay    = YES;

[eventStore saveEvent:event span:EKSpanThisEvent error:nil];

Inserting Events with EventKitUI

Instead of saving the created event directly into the event store, a better approach is to use EventKitUI which will allow the user visually check/modify an event before it is inserted.

EKEventStore * eventStore = [[EKEventStore alloc] init];

EKEvent * event = [EKEvent eventWithEventStore:eventStore];
event.title     = title;
event.location  = location;
event.startDate = startDate;
event.endDate   = endDate;
event.notes     = notes;

EKEventEditViewController *controller = [[EKEventEditViewController alloc] init];

controller.eventStore       = eventStore;
controller.event            = event;
controller.editViewDelegate = self;

[self presentModalViewController:controller animated:YES];

[controller release];
[eventStore release];

If you use EventKitUI, remember to always set the editViewDelegate delegate, and implement a delegate method to handle the dismissal of the view controller window.

-(void)eventEditViewController:(EKEventEditViewController *)controller
         didCompleteWithAction:(EKEventEditViewAction)action {
    
    switch (action) {
       case EKEventEditViewActionCanceled:
           // User tapped "cancel"
           break;
       case EKEventEditViewActionSaved:
           // User tapped "save"
           break;
       case EKEventEditViewActionDeleted:
           // User tapped "delete"
           break;
       default:
           break;
    }
    
    [self dismissModalViewControllerAnimated:YES];
}

Resources

How to install APC on OS X (10.6)

2011-05-29T00:00:00-07:00

There are two ways to install APC on OS X 10.6 (Snow Leopard). The easy way, and the manual way. Thanks goes to @j_cartledge for the tipoff on the how to do it the easy way.

Easy Install

The easiest way to get running with APC is to use homebrew. If you already have this installed, just type:

brew install apc

The brew formula may ask you to do some additional steps like update your php.ini and restart apache. Otherwise that's it.

Manual Install

Here are the steps I took to compile and install APC on my machine running OS X 10.6 (Snow Leopard). I found a lot of inconsistent information on how to install APC manually, so hopefully this will work for you.

Step 1, install Xcode if it's not already installed.

Step 2, PCRE is is a prerequisite for installing APC, so it needs to be installed next:

Download the latest version of PCRE, and unpack it somewhere handy.
Using terminal, cd to the unpacked PCRE directory.
Run: ./configure --prefix=/usr/local
Run: make
Run: sudo make install

Step 3, install APC:

Download the latest copy of APC, and unpack it somewhere handy.
Using terminal, cd to the unpacked APC directory.
Run: /usr/bin/phpize
Run: MACOSX_DEPLOYMENT_TARGET=10.6 CFLAGS="-arch x86_64 -g -Os -pipe -no-cpp-precomp" CCFLAGS="-arch x86_64 -g -Os -pipe" CXXFLAGS="-arch x86_64 -g -Os -pipe" LDFLAGS="-arch x86_64 -bind_at_load" ./configure --enable-apc-spinlocks
Run: make
Run: sudo make install

Step 4, update your settings:

Open (or create) your /etc/php.ini file in a text editor and add a reference to APC: extension=/usr/lib/php/extensions/no-debug-non-zts-20090626/apc.so
Restart apache: sudo httpd -k restart
Test APC is installed: php -i | grep "APC"

Was this helpful? Please leave a comment if these instructions worked for you. If you needed to take alternate steps to get this installed, please leave a comment on what you did differently and what issue it resolved. Thanks!

Stop safari's toolbar being hidden

2011-04-30T00:00:00-07:00

It really annoys me when a site forces you to open a web page in a new window. It really really really really really annoys me when that new window has no toolbar, status bar, bookmarks bar, scroll bars, has been moved, resized or stops you from resizing it.

That is why I've put together an open source safari 5 extension called "WindowControl", that disables web pages from doing this.

WindowControl gives users back the power to control how their browser windows look and behave. New windows will still open, only the child windows will look like their parent windows. No alterations.

You can download the FREE safari extension here.

Update: I've added toggable settings to the extension, so you can choose which parts of your browser window scripts can alter.

Scheduled Shutdown on OS X

2011-02-24T00:00:00-08:00

I found a mac app (actually two) on the App Store, that allow you to set a timer for when you want your mac to shutdown, restart, sleep or logout. I thought this would be an easy app to build so I attempted my own.

I considered posting the instructions on how to write this app, but it is really simple to implement. In fact, Apple provide you with the most important part of the code.

So instead I am just going to open source the code for this app, and let you lol at the simplicity.

If you are a good (or just better then me) interface designer, feel free to modify the interface into something nicer and get it onto the App Store as a free download.

I've also made available an universal binary of the app. Enjoy.

How to write a password generator

2011-02-22T00:00:00-08:00

I noticed on the recently released mac app store, there are some very simple apps which are being sold for $1 or more. So I thought I would write my own version of these apps and explain how they work.

Let's take a look at how to write a simple password generator. The source for this project can be found on github.

Password generator

For this project I wanted the user to be able to select the types of symbols that will appear in the password. I'm going to assume you are already familiar with setting up interfaces and connecting them with IBOutlets and IBActions (if not, examine the provided source code).

NB: Although this is an objective-c project, I've dropped back to C to do do most of the work. Manipulating characters in c-strings is very efficient and simple.

The first step is to determine how long the password will be, and what characters it will be built from:

int letters  = ...; // set these values from your input controls
int capitals = ...;
int digits   = ...;
int symbols  = ...;
int length   = letters + capitals + digits + symbols;

char *lettersAlphabet  = "abcdefghijklmnopqrstuvwxyz";
char *capitalsAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char *digitsAlphabet   = "0123456789";
char *symbolsAlphabet  = "!@#$%*[];?()";

Then declare an empty string of the right length which we will fill with these random characters. We will also need a second char pointer that points to this string:

// Build the password using C strings - for speed
char *cPassword = calloc(length + 1, sizeof(char));
char *ptr       = cPassword;

cPassword[length - 1] = '\0'; // terminate the c-string

Now for each alphabet set, we will need to add the required amount of symbols. I've used a helper function to reduce duplication:

ptr = appendRandom(ptr, lettersAlphabet, letters);
ptr = appendRandom(ptr, capitalsAlphabet, capitals);
ptr = appendRandom(ptr, digitsAlphabet, digits);
ptr = appendRandom(ptr, symbolsAlphabet, symbols);

This is what the helper function looks like:

char *appendRandom(char *str, char *alphabet, int amount) {
  for (int i = 0; i < amount; i++) {
    int r = arc4random() % strlen(alphabet);
    *str = alphabet[r];
    str++;
  }
  
  return str;
}

Notice how it advances the string pointer after it appends each character? This is why we needed to create the second char pointer.

Next, we rearrange the symbols in the string so the different alphabet types aren't grouped together:

for (int i = 0; i < length; i++) {
  int  r    = arc4random() % length;
  char temp = cPassword[i];
  cPassword[i] = cPassword[r];
  cPassword[r] = temp;
}

Finally, convert the c-string back into an objective-c string, and don't forget to free any allocated memory.

NSString *thePassword = [NSString stringWithCString:cPassword encoding:NSUTF8StringEncoding];

free(cPassword);

See! I told you it was simple, and you've saved yourself a dollar.

Download the full code for this project from github.

A new design

2011-01-25T00:00:00-08:00

Don't adjust your computer screens, this is still neilang.com. For the fourth time I've rebuilt my blog (or should I say "Plog"). Now with even less features!

Notable changes include:

Less navigation
Less content
New HTML5 layout
Running on Jekyll (previously Symphony)
Hosted on github.com
Comments by Disqus
Dropped support for IE6, IE7 and FF2.

Redirect to iPhone site with htaccess

2010-02-06T00:00:00-08:00

This is my implementation of how to redirect to an iPhone optimised website using Apache rewrite rules and cookies. Although this redirect can be achieved easily through server-side scripting, websites that implement heavy page caching need to redirect at the request level.

The interaction: If the user is using an iPhone to view the site, I wanted to automatically redirect them to the iphone site, however I also wanted to allow the user to switch between the two versions of the website freely - and to remember their preference for which version of the site they wanted to view when they returned. I also didn't want to embed absolute URLs into links or append parameters to the end of urls.

So these are the rules I came up with to redirect an iphone visiting www.example.com to i.example.com. On each page of the site I include a link to switch between the two sites. Example. If the user is viewing i.example.com/about.html there would be a server relative link to "/noiphone/about.html" and on the normal site there would be a link to "/iphone/about.html" etc.

# Always redirect to the iphone site (unless there is a cookie)
RewriteCond %{HTTP_USER_AGENT} iPhone 
RewriteCond %{HTTP_HOST} !^i.example.com 
RewriteCond %{HTTP_COOKIE} !^.*no_iphone=yes.*$ [NC] 
RewriteRule ^/(.*)$ http://i.example.com/$1 [R,L] 

# User requested normal site (sets cookie) 
RewriteCond %{REQUEST_URI} ^/noiphone/.*$ 
RewriteRule ^/noiphone/(.*)$ http://www.example.com/$1 [R,L,CO=no_iphone:yes:.example.com:10080] 

# User requested iphone site (removes cookie) 
RewriteCond %{REQUEST_URI} ^/iphone/.*$ 
RewriteRule ^/iphone/(.*)$ http://i.example.com/$1 [R,L,CO=no_iphone:0:.example.com:-1]

You may notice that the cookie expire time to remember their preference is set to 10080 minutes (1 week), you may want to adjust this if you don't want their preference to expire.

How to create a spell checking web spider

2009-08-24T00:00:00-07:00

Recently I found out my employer was paying a third-party company to regularly check the spelling on their website and send them a monthly report. So I thought I would write a simple spider that could to do the same thing and save them money.

The setup

My solution uses ruby (plus some gems) and the awesome Aspell (an open source spell checker).

First of all you will need to download and install Aspell, and an Aspell dictionary for the language you want to use. In this example I will be using the English dictionary.

To install Aspell on OS X, download and unpack the latest version, and then using terminal:

cd path/to/aspell ./configure make sudo make install

To install a dictionary, repeat the steps above with a downloaded dictionary.

You can verify that Aspell installed correctly and that the dictionaries are loaded by typing these commands in terminal:

aspell -v aspell dicts

Next you will need to install raspell, which is a gem used to interact with Aspell. You will also need another gem called spider, which will take care of the web crawling work for us. And finally, hpricot or nokogiri to handle the HTML.

sudo gem install raspell sudo gem install spider sudo gem install hpricot

The script

With that done, you can use the spider gem to crawl all the html pages on a website, then use hpricot to extract the relevant words from the page and check each one with raspell. E.g.

#!/usr/bin/env ruby 

require 'rubygems' 
require 'spider' 
require 'raspell' 
require 'hpricot' 

domain = 'http://www.example.com/' 

speller = Aspell.new('en_GB') 

Spider.start_at(domain) do |s| 

  s.add_url_check do |a_url| 
    a_url.match("^#{domain}") 
  end 

  s.on :success do |a_url, resp, prior_url| 
    unless resp['content-type'].match('text/html') 
      puts "Skipping #{a_url}" 
      next 
    end 
    puts "On page #{a_url}" 
     
    document = Hpricot(resp.body) 
    document.search('head').remove 
    document.search('script').remove 
    document.search('link').remove 
    document.search('meta').remove 
    document.search('style').remove 
    words = document.inner_text.gsub(/\s+/, ' ').strip.split(/\s/) 
     
    speller.list_misspelled(words).each do |mistake| 
      puts " * Found mistake \"#{mistake}\" perhaps you meant \"#{speller.suggest(mistake).first}\"" 
    end 
  end 

end

A few things to note about this script:

I have set the spider to use the "en_GB" dictionary (as this is what we use in Australia), but you can set it to any dictionary you installed (e.g. "en_US").
If you wanted to use nokogiri instead of hpricot, simply replace the Hpricot declaration with document = Nokogiri(resp.body) and require it at the start of the script.
Hpricot is used to strip out typically non-visible sections of the page, so that we only spellcheck the displayed words.
The spider won't search outside of the set domain.
The spider is also capable of performing a link check as it crawls.

As you can see this is only a very basic implementation, but demonstrates how easily you can create your own spelling spider!

Validate an ISSN using Perl

2009-06-12T00:00:00-07:00

Last week I wrote about validating an ISBN, so this week I thought I would post the code to validate an ISSN.

There are only a few minor differences between validating an ISSN and ISBN.

sub valid_issn { 
  my $issn = $_[0]; 
     $issn =~ s/[^\dX]//gi; 
  return if length($issn) != 8; 
  my $sum = 0; 
  my @chars = split('', $issn); 
  $chars[7] = 10 if uc($chars[7]) eq 'X'; 
  for (my $char = 0; $char < @chars; $char++) { 
    $sum += (8-$char) * $chars[$char]; 
  } 
  return (($sum % 11) == 0); 
}

Validate an ISSN using JavaScript

2009-06-12T00:00:00-07:00

Last week I wrote about validating an ISBN, so this week I thought I would post the code to validate an ISSN.

There are only a few minor differences between validating an ISSN and ISBN.

function isValidISSN (issn) { 
  issn = issn.replace(/[^\dX]/gi, ''); 
  if(issn.length != 8){ 
    return false; 
  } 
  var chars = issn.split(''); 
  if(chars[7].toUpperCase() == 'X'){ 
    chars[7] = 10; 
  } 
  var sum = 0; 
  for (var i = 0; i < chars.length; i++) { 
    sum += ((8-i) * parseInt(chars[i])); 
  }; 
  return ((sum % 11) == 0); 
}