Class: GObject::GObject

Inherits:

Object

• Object
• GObject::GObject

Extended by:

Forwardable, SingleForwardable

Defined in:

lib/vips/gobject.rb

Overview

we have a number of things we need to inherit in different ways:

• we want to be able to subclass GObject in Ruby in a simple way
• the layouts of the nested structs need to inherit
• we need to be able to cast between structs which share a base struct without creating new wrappers or messing up refcounting
• we need automatic gobject refcounting

the solution is to split the class into four areas which we treat differently:

• we have a "wrapper" Ruby class to allow easy subclassing ... this has a @struct member which holds the actual pointer
• we use "forwardable" to forward the various ffi methods on to the @struct member ... we arrange things so that subclasses do not need to do the forwarding themselves
• we have two versions of the struct: a plain one which we can use for casting that will not change the refcounts
• and a managed one with an unref which we just use for .new
• we separate the struct layout into a separate module to avoid repeating ourselves

Direct Known Subclasses

Vips::Object

Defined Under Namespace

Modules: GObjectLayout Classes: ManagedStruct, Struct

Instance Attribute Summary

• #ptr ⇒ Object readonly

  get the pointer we were built from ...

• #references ⇒ Object readonly

  Returns the value of attribute references.

Class Method Summary

• .ffi_managed_struct ⇒ Object
• .ffi_struct ⇒ Object

Instance Method Summary

• #ffi_managed_struct ⇒ Object

  access to the managed struct for this class.

• #ffi_struct ⇒ Object

  access to the casting struct for this class.

• #initialize(ptr) ⇒ GObject constructor

  don't allow ptr == nil, we never want to allocate a GObject struct ourselves, we just want to wrap GLib-allocated GObjects.

Constructor Details

#initialize(ptr) ⇒ GObject

don't allow ptr == nil, we never want to allocate a GObject struct ourselves, we just want to wrap GLib-allocated GObjects

here we use ManagedStruct, not Struct, since this is the ref that will need the unref

# File 'lib/vips/gobject.rb', line 75

def initialize ptr
  # GLib::logger.debug("GObject::GObject.initialize") {"ptr = #{ptr}"}
  @ptr = ptr
  @struct = ffi_managed_struct.new ptr

  # sometimes we need to keep refs across C calls ... hide them here
  @references = []
end

Instance Attribute Details

#ptr ⇒ Object (readonly)

get the pointer we were built from ... #to_ptr gets the pointer after we have wrapped it up with an auto unref

# File 'lib/vips/gobject.rb', line 91

def ptr
  @ptr
end

#references ⇒ Object (readonly)

Returns the value of attribute references.

# File 'lib/vips/gobject.rb', line 40

def references
  @references
end

Class Method Details

.ffi_managed_struct ⇒ Object

# File 'lib/vips/gobject.rb', line 105

def ffi_managed_struct
  const_get :ManagedStruct
end

.ffi_struct ⇒ Object

# File 'lib/vips/gobject.rb', line 94

def ffi_struct
  const_get :Struct
end

Instance Method Details

#ffi_managed_struct ⇒ Object

access to the managed struct for this class

# File 'lib/vips/gobject.rb', line 100

def ffi_managed_struct
  self.class.ffi_managed_struct
end

#ffi_struct ⇒ Object

access to the casting struct for this class

# File 'lib/vips/gobject.rb', line 85

def ffi_struct
  self.class.ffi_struct
end