Launching an Mac App with Objective-C/Cocoa

if(![[NSWorkspace sharedWorkspace] launchApplication:@"Path Finder"])
    NSLog(@"Path Finder failed to launch");

With Parameters:

NSWorkspace *workspace = [NSWorkspace sharedWorkspace];
NSURL *url = [NSURL fileURLWithPath:[workspace fullPathForApplication:@"Path Finder"]];
//Handle url==nil
NSError *error = nil;
NSArray *arguments = [NSArray arrayWithObjects:@"Argument1", @"Argument2", nil];
[workspace launchApplicationAtURL:url options:0 configuration:[NSDictionary dictionaryWithObject:arguments forKey:NSWorkspaceLaunchConfigurationArguments] error:&error];
//Handle error

You could also use NSTask to pass arguments:

NSTask *task = [[NSTask alloc] init];
NSBundle *bundle = [NSBundle bundleWithPath:[[NSWorkspace sharedWorkspace] fullPathForApplication:@"Path Finder"]]];
[task setLaunchPath:[bundle executablePath]];
NSArray *arguments = [NSArray arrayWithObjects:@"Argument1", @"Argument2", nil];
[task setArguments:arguments];
[task launch];

Based on yuji's answer in different posting, NSWorkspace is the tool to use, and I could get the same result with only two lines of code.

The openFile can be used for passing the parameter to Path Finder, which is normally the directory, not a file. However, it works fine.

[[NSWorkspace sharedWorkspace] openFile:string2 withApplication:@"Path Finder"];
[[NSApplication sharedApplication] terminate:nil];