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   1 <html><head><title>Cycript</title>
   2 </head><body>
   3
   4 <h1>Cycript: Objective-JavaScript</h1>
   5
   6 <h3>What is Cycript?</h3>
   7
   8 <p>A programming language designed to blend the barrier between Objective-C and JavaScript. This project has similar goals to JSCocoa, but a very different set of starting technologies and a different guiding philosophy. In particular, Cycript has started life with a full-blown JavaScript parser/serializer, allowing it to have interesting hybrid syntax without constraints (such as those imposed on JSCocoa by JSLint).</p>
   9
  10 <h3>Is it done?</h3>
  11
  12 <p>Well, it works ;P. It is still "in flux": core language features are changing every few hours. However, it has already changed the workflow of the "elite" iPhone developers that write most of the extensions you see in Cydia: having a language that changes doesn't matter when you are mostly using it at the immediate console. I'm hoping, however, that I manage tolock it into something that feels "correct" in the very near future.</p>
  13
  14 <h3>How do you pronounce "Cycript"?</h3>
  15
  16 <p>I pronounce it "sscript" (with a geminate, aka long, 's'). I doubt anyone else will pronounce it like this, but I have my hopes.</p>
  17
  18 <h3>Where do I get it?</h3>
  19
  20 <p>Right now you can find releases of it at: <a href="http://www.cycript.org/debs/">http://www.cycript.org/debs/</a>. This package depends on MobileSubstrate and libffi (both of which are in Cydia).</p>
  21
  22 <h3>So, how do I use it?!</h3>
  23
  24 <p>Although you can write full applications in Cycript, the fastest way to get playing with it is via the immediate console: just type "cycript".<p>
  25
  26 <xmp>iPhone:~$ cycript
  27 cy# </xmp>
  28
  29 <p>Code typed at this prompt will be executed as it is able to be parsed: the immediate console is trying to eagerly parse lines of code as they come in (and thereby is not subject to automatic-semicolon insertion, for those JavaScript experts). Parse errors will be noted to the output in a hopefully useful fashion.</p>
  30
  31 <xmp>cy# function a() {
  32 cy>    a + q r
  33   | .........^
  34   | syntax error, unexpected Identifier, expecting ; or "\n"
  35 cy# </xmp>
  36
  37 <p>It should be noted that it is possible that you will manage to break my JavaScript serializer. In these cases, parse errors may be thrown by the underlying JavaScript engine rather than Cycript. To debug these issues you can use the special console command ?debug.</p>
  38
  39 <xmp>cy# ?debug
  40 debug == true
  41 cy# var a = ((0 + (1)) * (2 * 3)) + m['a']('\'')
  42 var a=(0+1)*(2*3)+m.a("'");
  43 ...</xmp>
  44
  45 <p>In addition to standard JavaScript, you an also access anything in the Objective-C runtime. Attempts have been made, sparingly, to bridge syntax when possible between the two environments. In particular, you may notice interesting properties of arrays, dictonaries, strings, and numbers. Care has been taken to minimize the damage to the object model.</p>
  46
  47 <xmp>cy# var a = [NSMutableArray arrayWithCapacity:4]
  48 cy# a instanceof Array
  49 true
  50 cy# [a class]
  51 "NSCFArray"
  52 cy# [a addObject:"hello"]; a
  53 ["hello"]
  54 cy# a[1] = 4; a.push(10); a
  55 ["hello",4,10]
  56 cy# a.splice(1, 1, 6, 7); a
  57 ["hello",6,7,10]
  58 cy# b = [1, 2]; [b replaceObjectAtIndex:0 withObject:5]; b
  59 [5,2]</xmp>
  60
  61 <p>Memory management is mostly automatic, but instead of using the usual -[alloc] message you will need to use JavaScript's "new" operator, which returns a special "uninitialized" handle that can be used to send a single message (probably a form of init) before it "expires" and reverts to nil.</p>
  62
  63 <xmp>cy# var a = new NSMutableDictionary
  64 cy# a
  65 "*** -[NSCFDictionary count]: method sent to an uninitialized mutable dictionary object"
  66 cy# var b = [a init]; b
  67 {}
  68 cy# a
  69 nil
  70 cy# var q = [new NSString init]; q
  71 ""</xmp>
  72
  73 <p>One note in particular is made about selectors. Not only do they act as in Objective-C, including being typed using @selector notation, but they also have Function.prototype in their prototype-chain, allowing you to use them in interesting functional ways ala JavaScript. You can also generate one from a string using new Selector().</p>
  74
  75 <xmp>cy# var sel = @selector(initWithFrame:)
  76 cy# sel
  77 @selector(initWithFrame:)
  78 cy# sel.call(new UIView, [UIHardware fullScreenApplicationContentRect])
  79 "<UIView: 0x22dae0; frame = (0 20; 320 460); layer = <CALayer: 0x209990>>"
  80 cy# new Selector("initWithFrame:")
  81 @selector(initWithFrame:)</xmp>
  82
  83 <p>As one would expect from JavaScript, objects have a property called constructor that references their class, and classes have a property called prototype that gives you access to their messages. These can even be traded around and reassigned, with the results fully mapping back to the Objective-C runtime.</p>
  84
  85 <xmp>cy# var view = [new UIView init]
  86 cy# view.constructor
  87 "UIView"
  88 cy# view.constructor.prototype.description
  89 0x309d84f5
  90 cy# [view description]
  91 "<UIView: 0x229bc0; frame = (0 0; 0 0); layer = <CALayer: 0x229d60>>"
  92 cy# view.constructor.prototype.description = function () { return "not!"; }
  93 {}
  94 cy# [view description]
  95 "not!"</xmp>
  96
  97 <p>Structures are also supported (although unions are currently on the todo list and bitfields are still DOA): they are bridged back/forth as much as possible. You can specify them using either array syntax or in the form of dictionaries.</p>
  98
  99 <xmp>cy# var rect = [UIHardware fullScreenApplicationContentRect]
 100 cy# rect
 101 {origin:{x:0,y:20},size:{width:320,height:460}}
 102 cy# rect.origin = [2, 3]
 103 [2,3]
 104 cy# rect.size = {width: 0, height: 1}
 105 {width:0,height:1}
 106 cy# rect
 107 {origin:{x:2,y:3},size:{width:0,height:1}}</xmp>
 108
 109 <p>Access, allocation, and casting of pointers is possible through the usage of the Pointer and Type classes. Pointers can be indirected using the * and -> operators, as in C.</p>
 110
 111 <xmp>cy# var count = new new Type("I")
 112 cy# var methods = class_copyMethodList(UIApplication, count)
 113 cy# *count
 114 305
 115 cy# *new Pointer(count, "d")
 116 7.304555902977629e-304
 117 cy# free(count)
 118 cy# methods
 119 0x843800
 120 cy# methods[304]
 121 0x825248
 122 cy# method_getName(methods[304])
 123 @selector(init)</xmp>
 124
 125 <p>Objective-C @properties (some of which are auto-detected, as Apple doesn't always compile them into the resulting binaries) can be accessed using . notation. Currently, auto-detected @properties are usable, but aren't enumerable. This namespace is strictly separated from that of instance variables, which you can access by indirecting the object using * or ->.</p>
 126
 127 <xmp>cy# var view = [new UIView init]
 128 cy# ps = []; for (var p in view) ps.push(p); ps
 129 ["skipsSubviewEnumeration","gestureRecognizers","gesturesEnabled","capturesDescendantTouches","deliversTouchesForGesturesToSuperview","userInteractionEnabled","layer","tag"]
 130 cy# vs = []; for (var v in *view) vs.push(v); vs
 131 ["isa","_layer","_tapInfo","_gestureInfo","_gestureRecognizers","_charge","_tag","_viewFlags"]
 132 cy# view.layer
 133 "<CALayer: 0x228f60>"
 134 cy# view->_layer
 135 "<CALayer: 0x228f60>"
 136 cy# (*view)._layer
 137 "<CALayer: 0x228f60>"</xmp>
 138
 139 <p>Fully-fledged Objective-C classes can also be declared using @class, which blurs the line between Objective-C's @interface and @implementation. Right now, declaring instance variables are not supported, but will be in a future version: for now you must provide an empty variable block.</p>
 140
 141 <xmp>cy# @class TestClass : NSObject {
 142 cy> }
 143 cy> - description {
 144 cy>     return "test";
 145 cy> }
 146 cy> @end
 147 cy# [new TestClass init]
 148 "test"</xmp>
 149
 150 <p>The @class syntax can also be used to extend existing classes in a manner similar to categories. Note that type signatures, however, are not yet supported, so you end up heavily restricted in what you can add via this mechanism. In this case, one can also use a parenthesized expression as the class name.</p>
 151
 152 <xmp>cy# @class NSObject
 153 cy> - description { return "replaced"; }
 154 cy> @end
 155 cy# var o = [new NSObject init]
 156 cy# o
 157 "replaced"
 158 cy# @class ([o class]) - description { return "again"; } @end
 159 cy# o
 160 "again"</xmp>
 161
 162 <p>Cycript is also capable of accessing normal C functions and variables. Knowledge of the type signatures of various functions are provided in the bridge definition file, which is currently a plist stored at /usr/lib/libcycript.plist.</p>
 163
 164 <xmp>cy# malloc
 165 0x31d48389
 166 cy# var p = malloc(4)
 167 cy# p
 168 0x22e0a0
 169 cy# free(p)
 170 cy# </xmp>
 171
 172 <p>Cycript attempts to do its best to serialize information to the console about objects. In particular, CoreFoundaton objects bridged to Objective-C are detected and printed using CFCopyDescription.</p>
 173
 174 <xmp>cy# UIGetScreenImage()
 175 "<CGImage 0x22f540>"
 176 cy# ABAddressBookCreate()
 177 "<ABCAddressBook 0x229cf0 [0x38208484]>"</xmp>
 178
 179 <h3>How do I write an application with it?</h3>
 180
 181 <p>This isn't quite "ready for primetime", but you can download the example HelloCycript.app from <a href="http://www.cycript.org/examples/">http://www.cycript.org/examples/</a> and put it in /Applicatons.</p>
 182
 183 <h3>What else can it do?</h3>
 184
 185 <p>Probably the awesomest thing you can do with Cycript is to hook into an existing process using the -p argument to the console interpreter. As an example, let's hook our way into SpringBoard and start spelunking.</p>
 186
 187 <xmp>iPhone:~$ ps ax | grep Spring
 188 18110   ??  Us     0:03.03 /System/Library/CoreServices/SpringBoard.app/SpringBoard
 189 18115 s006  S+     0:00.02 grep --color=auto --exclude=.svn Spring
 190 iPhone:~$ cycript -p 18110
 191 cy# UIApp
 192 "<SpringBoard: 0x266f00>"
 193 cy# UIApp->_uiController.window
 194 "<SBAppWindow: 0x27ac10; baseClass = UIWindow; frame = (0 0; 320 480); layer = <CALayer: 0x27aba0>>"
 195 cy# UIApp->_uiController.window.subviews
 196 ["<UIView: 0x4a6efa0; frame = (0 0; 320 480); autoresize = W+H; layer = <CALayer: 0x4a62d70>>","<SBAppContextHostView: 0x49a68f0; frame = (0 0; 320 480); clipsToBounds = YES; hidden = YES; layer = <CALayer: 0x2b4d10>> enabled: yes, context array: (\n)","<SBAppContextHostView: 0x4b5ccf0; frame = (0 0; 320 480); clipsToBounds = YES; hidden = YES; layer = <CALayer: 0x4b7f180>> enabled: yes, context array: (\n)"]
 197 cy# UIApp->_uiController.window.subviews[0].subviews
 198 ["<UIImageView: 0x4b3cea0; frame = (0 0; 320 480); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x4a75550>>","<UIView: 0x4b4ba80; frame = (0 0; 320 480); autoresize = W+H; layer = <CALayer: 0x4b4bbf0>>"]
 199 cy# UIApp->_uiController.window.subviews[0].subviews[0].image.size
 200 {width:320,height:480}
 201 cy# UIApp->_uiController.window.subviews[0].subviews[1].subviews
 202 ["<SBIconContentView: 0x4b4bc20; frame = (0 40; 320 349); autoresize = H; layer = <CALayer: 0x4a613c0>>","<UIView: 0x4a25250; frame = (0 389; 320 91); layer = <CALayer: 0x4a38630>>"]
 203 cy# UIApp->_uiController.window.subviews[0].subviews[1].subviews[0].subviews
 204 ["<SBIconListPageControl: 0x27aab0; baseClass = UIPageControl; frame = (0 330; 320 19); autoresize = TM; layer = <CALayer: 0x4b3c370>>","<SBIconScrollView: 0x4a62360; baseClass = UIScrollView; frame = (0 0; 320 330); autoresize = H; layer = <CALayer: 0x4a624e0>>"]
 205 cy# var pages = UIApp->_uiController.window.subviews[0].subviews[1].subviews[0].subviews[0]
 206 cy# pages.currentPage
 207 1
 208 cy# pages.numberOfPages
 209 15</xmp>
 210
 211 </body></html>