apple.com 2011-10-05 at 10.43.35 PM

It’s weird. I’ve never had the privilege to work for Steve Jobs, let alone meet him or know him, yet it feels like someone close died.

I was reflecting earlier on the fact that he is one of childhood heroes. From way back when I was a penny-less teenager, I was dreaming about owning a Macintosh and program for it. Or make music with it. Or just play games. And soon later came the absurd NeXT cube, with its black magnesium body. Oh, how I loved that thing. And its beautifully architected operating system. And this weird language no-one else was using, Objective-C.

The world lost a complex visionary. The one who declared floppy disks obsolete in circa 1989. The man who gave a name to those weird devices called “MP3 players” that nobody – nobody, I swear! – was using before the iPod. The guy who made me love iOS even if I hated its closed architecture. And the wise who insisted on the simplicity of single-button mice. Not forgetting the businessman unafraid to admit his LSD experiences.

Most importantly, he made me understand that engineering can meet with art and idealism. He is not the only one who has done it, but he is the only one that lived during my lifetime.

So, thank you Steve Jobs.

1. open Project settings and choose “Latest iOS” under Base SDK for All Configurations
2. open your target and make sure the settings applies to it (in case you overrode it)
3. (yes, somehow the “Base SDK Missing” error seems to stick)
4. shutdown Xcode and reopen.

The SDK now is set.

I just spent the last 20 minutes baffled by some weird errors as I was building Erlang on an OpenBSD box I am setting up.

$ make
make: "/home/acces/otp_src_R13B04/Makefile" line 88: Missing dependency operator
make: "/home/acces/otp_src_R13B04/Makefile" line 89: Missing dependency operator
...
100 similar lines follow
...

The problem is… that when you type make, OpenBSD — and probably NetBSD and FreeBSD — all use BSD make by default, NOT GNU make! Silly me. I even had just installed GNU make a couple hours earlier!

So anyway:

$ pkg_add -i -v gmake
...
[download, unzip, configure Erlang OTP]
...
$ make # WILL FAIL!
$ gmake

Beside importing SimpleTimer (my first Cocoa app: beware, its code might not be the prettiest!), this is the first release of CLutils, my collection of C/C++/Objective-C functions built over the years. There’s not much structure in it, beside subdividing it by deployment platforms (Mac OS X, iOS and cross-platform code) and OS X APIs (Carbon, Cocoa).

http://github.com/ettore/SimpleTimer/
http://github.com/ettore/CLutils/

compile error:
1071: Syntax error: expected a definition keyword (such as function) after attribute override, not protected.

in relation to the following code:

override
protected function createChildren():void {}

The solution?

override protected function createChildren():void {}

Don’t even get me started.

1. Login into the Provisioning Portal, click “App IDs” on the left side column
2. Click “Configure” on the App ID of your app
3. Click Revoke for the expired Push SSL certificate
4. Open Keychain Access on your Mac. Click the “Certificates” category, find the expired cert and just delete it.
5. From the Provisioning Portal website, start creating a brand new Push SSL certificate. Just follow the instructions.
6. Don’t forget to download the signed cert and double-click it to install it (aps_developer_identity.cer) in your default keychain.
7. Find the newly created cert in Keychain Access and click the disclose triangle. Then:
   • - Right-click on the private key entry without selecting the parent, and select Export. A .p12 file will be saved
   • - Right-click on the actual certificate without selecting the child key, and select Export. Another .p12 file will be saved
8. If your server requires .pem style certificates, run this:

   $ openssl pkcs12 -in apn_cert.p12 -out apn_cert.pem -nodes
   $ openssl pkcs12 -in apn_key.p12 -out apn_key.pem -nodes
   

9. Deploy the .pem files in the right location accessible by your application server that will be sending the Push notifications.

Now push notifications should be up and running once again.

1. Login into the Provisioning Portal, click “Provisioning” on the left side column
2. Renew your expired profile (or create new one) and download it
3. Drag it over the Xcode dock icon (or add it into the Organizer)
4. Remove old profiles from Xcode Organizer
5. Open your Device target. Select the Build tab -> Code Signing Identity, and make sure the new profile is the one in use.
   Xcode has the habit of not automatically updating its targets to use the newly installed provisioning profile. (Even if you physically removed the old one.)

At this point you should be able to rebuild the app.

Some examples:

1> <<2#11110000:5>>.
< <16:6>>
2> <<2#11110000:6>>.
< <48:6>>
3> erlang:is_bitstring(<<2#11110000:6>>).
true
4> erlang:is_binary(<<2#11110000:6>>).
false
5> erlang:is_bitstring(<<2#11110000:8>>).
true
6> erlang:is_binary(<<2#11110000:8>>).
true

In the Erlang bit syntax there are 2 clarifying (?) type synonyms:

bytes == binary
bits  == bitstring

which are basically telling you to think of binaries as sequence of bytes, and bitstrings as sequence of bits. Quite obvious right? Well, it wasn’t for me at first.

It’s also worth noting how binaries and bitstrings are converted into text strings. Given the binary <<16#50>> storing the letter ‘P’,

7> <<16#50>>
<<"P">>
8>erlang:bitstring_to_list(<<16#50>>). #I could've used binary_to_list()
"P"          %great!
9>erlang:bitstring_to_list(<<16#50:5>>).
[<<16:5>>]  %mmh...

The result of command #9 is not exactly what I had imagined. Yes, it’s a list, but it’s certainly not a text string, and I was expecting a text string. Why was I expecting a text string if the API is named bitstring_to_list() ? Because if I was in the middle of coding a text manipulation algorithm and called bitstring_to_list(), I would probably (wrongly) assume that it would do some magic and transform any bitstring in a usable text string. Why? Because we are used to treat text strings as lists. Why? Because we don’t have APIs that mention “strings”: all the builtin APIs only mention lists. That’s the problem. We are using a list API as if it was a string API, when a generic list is not necessarily a string.

My first reaction was “I’m going to put all possible states since I just want the button title to change no matter what.” So I blindly bit-OR‘ed all the possible values defined in the docs.

[myButton setTitle:@"New Title"
          forState:UIControlStateNormal | UIControlStateHighlighted | UIControlStateDisabled | UIControlStateSelected];

Sound reasonable right? Wrong. If you do that here, your button title is probably not going to change at all. The problem is that the “normal” state (per Apple docs that’s “enabled, not selected, not highlighted”) is defined as such:

enum {
    UIControlStateNormal   = 0,
    UIControlStateHighlighted  = 1 << 0,
    UIControlStateDisabled     = 1 << 1,
    UIControlStateSelected     = 1 << 2,
    ...
}

so if you bit-OR all of them you are actually going to set the title for ALL states EXCEPT the “normal” (most common) state!

Sigh…

Anyway. Here’s some binary data in Erlang:

<<16#1192c05a:32>>

What does all this mean? Let’s analyze it, left to right.

1. 16# This specifies we want to express the number in base 16.
2. We have an eight digits hex number.
3. No type specification is provided: default is unsigned integer.
4. No unit specification is provided: default for integer is 1, which means ‘bits’.
5. :32 Size specification: this tells erlang to consider 32 units, which in our case means 32 bits, since we are dealing with bits.

Let’s evaluate it:

86> <<16#2092105a:32>>.
<<32,146,16,90>>

What if we forget to specify the size spec? In that case the default will apply and since we’re dealing with an integer type, the default is 8 (bits). For Erlang this means we are going to return the least significant byte:

87> <<16#2092105a>>.
<<90>>

Now that we know that, we can get a subset of bits by setting the size accordingly:

88> <<16#2092105a:16>>.
<<16,90>>     %two least significant bytes

We don’t need to specify a size multiple of 8:

89> <<16#1192FFFF:15>>.
<<255,127:7>>

It’s pretty cool how easy it is to slice bytes apart at the bit level. I was sort of surprised that if we slice some internal bits it looks like the bits at the right are moved to the left. E.g. here we take the 4 least significant bits of the first 0xFF:

90> <<16#FF:4,0,16#FF,0>>.

but instead of obtaining:

<<16:4,0,255,0>>
F 00 FF 00

we get:

<<240,15,240,0:4>>
F0 0F F0 0          [240 == F0]

Also, the value doesn’t need to be a literal, it can be an expression:

91> N = 16#FF00FF01.
4278255361
92> <<N:32>>.
<<255,0,255,1>>

And therefore, given some binary data, we can also pattern-match it super easily:

<SourcePort:16, DestinationPort:16, CheckSum:16, Payload/binary>> = SomeBinary.

There’s more to Erlang bit syntax than this, but I’ll stop here for now.