MacRuby: The Definitive Guide: Ruby and Cocoa on OS X

New(:integer) s brief Pointer. new(:short) l lengthy Pointer. new(:long) C unsigned char Pointer. new(:uchar) I unsigned integer Pointer. new(:uint) S unsigned brief Pointer. new(:ushort) L unsigned lengthy Pointer. new(:ulong) f waft Pointer. new(:float) @ item Pointer. new(:object) or Pointer. new(:id) B Boolean Pointer. new(:boolean) # classification Pointer. new(:class) : selector Pointer. new(:selector) you could create guidelines by means of passing the logo identify as proven above, and in addition via passing the pointer style code as a string. you could dereference the pointer a similar means you entry an array in Ruby. you may also have a pointer to a number of values. here's the way you create a pointer with bounds: 158 | bankruptcy 8: One Step Deeper pointer = Pointer. new(:float, four) pointer[0] = 1. zero pointer[1] = 2. zero pointer[2] = three. zero pointer[3] = four. zero pointer[0] # => 1. zero pointer[1] # => 2. zero pointer[2] # => three. zero pointer[3] # => four. zero To assign a cost to the pointer, you should use this kind of equipment: pointer. assign(3. 2) # or pointer[0]= three. 2 if you use [] and []=, you need to be cautious to not try and entry or set a cost out of bounds. regrettably, there's no technique to discover a pointer’s bounds. Dereferencing tips is lovely effortless and used to be proven past: pointer = Pointer. new(:integer) pointer. assign(42) pointer[0] # => forty two you can even offset tips utilizing the + and the - equipment: pointer = Pointer. new(:long, 10) 10. times{|i| pointer[i] = i } pointer2 = pointer + 2 pointer2[0] # => 2 pointer2[1] # => three pointer2[2] # => four One scenario that calls for offsetting is while you're utilizing a learn procedure that accepts a pointer of bytes and returns the variety of bytes truly learn. you could set a pointer, cross it to the strategy, offset it, and go it back. here's a dummy instance of such an API: ptr = dataOut; fakeAPI(dataIn, dataInLength, ptr, dataOutAvailable &dataOutMoved); ptr += dataOutMoved; dataOutAvailable -= dataOutMoved; otherAPI(ptr, dataOutAvailable, &dataOutMoved); different types of Objective-C guidelines will not be at once supported via MacRuby: void tips and unknown style guidelines (also referred to as unsigned pointers). Let’s examine easy methods to paintings with those kinds. Void guidelines so much tools in APIs in keeping with CoreFoundation use tips to CFTypeRefs, which technically are tips to void (also often called void *). If a mode expects a void pointer argument, you could go a pointer of any style. tips | 159 Let’s examine an instance from the Accessibility API: extern AXError AXUIElementCopyAttributeValue ( AXUIElementRef point, CFStringRef characteristic, CFTypeRef *value); As you will find, this can be a C functionality that takes a pointer as its final argument. the cause of utilizing a pointer is that it'll carry the functionality end result after it’s known as and the caller can retrieve the outcome from the pointer. The striking factor with this functionality is that, as pointed out, it returns the retrieved information within the ultimate parameter (value), and hence calls for a pointer as that parameter. to exploit the strategy in MacRuby, create a variable (here named titlePtr) and assign it to an item pointer.