Being a newb so to speak in Objective-C it wasn’t an easy path to go down. Unfortunately Apple’s documentation leaves a lot to be desired, especially in regards to documenting what methods are inherited from parent classes. Thankfully I have a few OSX developer buddies who were able to come to my rescue a couple times. One really kewl tool I learned about in the process is called F-Script. It allows you to introspect applications as they are running and run scripts poking and prodding deep inside an application. This combined with class-dump provided me with the information I needed to be able to make my modifications.

Thankfully I knew a bit about method swizzling and how that works from a couple other previous pet projects I worked on. It’s still something I consider a black magic hack, but at least I was comfortable enough with the concept to know what to do. I’ve seen several ways of implementing method swizzling before, but I found the one inside ForgetMeNot and SIMBL’s documentation to be the simplest, so I used it instead of what I used previously.

The first thing I needed to do was figure out what created the URL that Safari used to load up the search results for a specific query. Digging around for a while using F-Script Anywhere, I found that was done by the URLWithSearchCriteria method of the GoogleSearchChannel class. I started off by writing a simple wrapper method which NSLog’d the input of the function as well as the output. After I learned what it did fully, I then wrote the following replacement method:

- (NSURL *)_jj_URLWithSearchCriteria: (NSString *)searchCriteria
{
NSURL *yurl = [NSURL URLWithString: [[NSString stringWithFormat:@"http://search.yahoo.com/search?p=%@", searchCriteria] stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]];
NSURL *url = [self _safari_URLWithSearchCriteria: searchCriteria];

NSLog(@"Search Criteria: %@", searchCriteria);
NSLog(@"Google URL: %@", url);
NSLog(@"Yahoo URL: %@", yurl);

return yurl;
}

I then needed to find a way to replace the placeholder text inside the SearchField with “Yahoo!” instead of “Google“. This unfortunately took a lot longer than I had hoped as I had trouble finding how to get access to the SearchField since it’s obviously not an easily accessible global variable or anything like that. Thankfully I finally was able to trace the stack and find it was defined inside _toolbarController in the BrowserWindowController class. I had already figured out how to set the text using F-Script, so it was a simple matter of finding a method to swizzle inside BrowserWindowController which would allow me to latch in. Viewing the class dump for Safari, I found my target pretty quickly, _setUpSearchField looked like a perfect candidate. Unfortunately I had trouble grabbing ahold of the private instance variable, but this was one of the spots where a buddy of mine was able to provide a solution. By using object_getInstanceVariable I was able to access it and thus could go on with my changes. Here’s the final replacement method which changes the “Google” placeholder text to “Yahoo!”:

- (void)_jj_setUpSearchField
{
// Call the "parent" first so it does it's business
[self _safari_setUpSearchField];

id _toolbarControllerObj;
object_getInstanceVariable(self, [@"_toolbarController" UTF8String], &_toolbarControllerObj);

// Now change the placeholder string from "Google" to "Yahoo!"
[[[_toolbarControllerObj searchField] cell] setPlaceholderString:@"Yahoo!"];

NSLog(@"Search placeholder string changed to Yahoo! from Google");
}

There are a few other spots which I could replace “Google” with “Yahoo!” (like the error dialog which happens when you press enter without typing anything or the toolbar editor), but I decided those weren’t important right now. If you would like to see the source code to this plugin, please go here:

http://safari-yahoo-search.googlecode.com/svn//trunk/YahooSearchPlugin/

You can also download the installer here (which also includes the source code inside the disk image):

http://safari-yahoo-search.googlecode.com/files/YahooSearchPlugin.dmg

Please note that while I work for Yahoo!, this plugin is not endorsed or supported in any way by my employer. Use is at your own risk and I make no guarantees it won’t blow up your computer, “eat babies” (stealing a term a coworker uses when an app does something bad), or generally cause you any multitude of different problems. You have been warned!

I’ll try and write up a good tutorial based on what I learned today in the near future. Please feel free to leave a comment with any comments, feedback, or questions and I will do my best to respond.

Update: This has only been tested on Safari 3.0.4 using SIMBL 0.82 on OSX 10.4.11 (aka Tiger). I will do my best to test this on Leopard as soon as possible.

Update: Since DreamHost is having serious performance issues today (first time it has been really bad for me, despite what others have experienced with them), I decided to copy the source code and download location over to Google Code. The URLs above have been updated above accordingly, please use them going forward.