Question

I’m wondering if it is possible to sort an NSArray of NSStrings based on a number value contained within. Basically its a list of process ID’s and process names, and I would like to sort the processes based on their process ID. The array looks like this :

"286             Google Chrome He",
"1209             ibtool",
"0             kernel_task",
"1             launchd",
"10             kextd",
"11             notifyd",
"12             diskarbitrationd",
"13             configd",
"14             syslogd",
"15             DirectoryService",
"16             distnoted",
"18             ntpd",
"22             SystemStarter",
"25             securityd",
"28             mds",
"29             mDNSResponder",
"30             loginwindow",
"31             KernelEventAgent",
"33             hidd",
"34             fseventsd",
"36             dynamic_pager",
"42             blued",
"43             autofsd",
"46             WDSmartWareD",
"47             WDDMService",
"61             coreservicesd",
"62             WindowServer",
"71             HWPortCfg",
"72             HWNetCfg",
"159             socketfilterfw",
"165             cvmsServ",
"177             coreaudiod",
"191             vmnet-bridge",
"196             vmnet-dhcpd",
"198             vmnet-netifup",
"200             vmnet-dhcpd",
"204             vmnet-natd",
"206             vmnet-netifup",
"220             launchd",
"224             Dock",
"225             SystemUIServer",
"226             Finder",
"228             pboard",
"229             fontd",
"240             UserEventAgent",
"247             AirPort Base Sta",
"252             iprint-listener",
"253             StatusMenu",
"254             Dropbox",
"271             dbfseventsd",
"275             Google Chrome",
"295             Google Chrome He",
"298             AppleSpell",
"634             Google Chrome He",
"696             Google Chrome He",
"730             Microsoft Word",
"733             Microsoft Databa",
"736             Microsoft AU Dae",
"1095             usbmuxd",
"1110             Xcode",
"1171             Interface Builde",
"1282             Interface Builde",
"1283             Interface Builde",
"1475             Google Chrome He",
"1531             Google Chrome He",
"1533             Google Chrome He",
"1681             Google Chrome He",
"1682             Google Chrome He",
"1686             Google Chrome He",
"1687             Google Chrome He",
"1692             Google Chrome He",
"1945             Google Chrome He",
"2088             Keynote",
"2268             Google Chrome He",
"2326             Google Chrome He",
"2481             Google Chrome He",
"2545             Google Chrome He",
"2596             Google Chrome He",
"2766             mdworker",
"2933             Google Chrome He",
"2963             iPhone Simulator",
"2967             SimulatorBridge",
"2970             lsd",
"2971             SpringBoard",
"2982             ocspd",
"2998             installd",
"3000             TableViewControl",
"3001             taskgated",
"3002             gdb-i386-apple-d"

Any help is very much appreciated!

Answer 1

Yes, you can use the following NSArray instance method:

- (NSArray *)sortedArrayUsingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context

You’ll need to define an int function that takes three arguments: two array elements to compare, and a context. It returns a NSComparisonResult (-1, 0 or 1). For example:

NSInteger firstWordIntCompare(id stringLeft, id stringRight, void *context)
{
    // Extract number from stringLeft and stringRight
    NSArray *wordsLeft = [stringLeft componentsSeparatedByString:@" "];
    NSArray *wordsRight = [stringRight componentsSeparatedByString:@" "];
    NSString *firstWordLeft = wordsLeft.count ? [wordsLeft objectAtIndex:0] : nil;
    NSString *firstWordRight = wordsRight.count ? [wordsRight objectAtIndex:0] : nil;
    int intLeft = [firstWordLeft intValue];
    int intRight = [firstWordRight intValue];

    if (intLeft < intRight)
        return NSOrderedAscending;
    else if (intLeft > intRight)
        return NSOrderedDescending;
    else 
        return NSOrderedSame;
}

Then return the sorted array by calling the NSArray method with your function:

NSArray *sortedArray = [origArray sortedArrayUsingFunction:firstWordIntCompare context:NULL];