Class: Autoload

• Inheritance
• Description
• Related information
• Class protocol
  • Signal constants
  • adding/removing autoloaded classes
  • fileOut
  • initialization
  • lazy compilation
  • loading
  • message catching
  • private
  • queries
  • utilities
• Subclasses

Inheritance:

   nil
   |
   +--Autoload

  This class inherits NOTHING - most messages will lead into doesNotUnderstand:

Package:

stx:libbasic

Category:

Kernel-Classes

Version:

rev: 1.180 date: 2018/08/28 09:30:07

user: cg

file: Autoload.st directory: libbasic

module: stx stc-classLibrary: libbasic

Author:

Claus Gittinger

Description:

Autoload is a stub for an 'as yet unloaded' class.

In memory limited systems (as my original 8Mb 386 system was),
all seldom-used classes were made subclasses of this class.
Autoload catches all messages sent to it, and files-in the real class's
code when first used. Then the caught message is resent to the (now existing) class.

A note from later days:
    These days, systems usually have enough memory to allow
    having all classes present, so many of the classes which used to be
    autoloaded are no longer these days. However, a number of examples or
    very seldom used frameworks are still present as autoloaded.
    Instead of using autoloaded classes, it is now recommended to bundle
    extra classes into packages, which are loaded en-bloque.
    Packages can be compiled to a shared class library and thus be loaded
    much faster (there is no need to parse and compile source files).

Lazy loading:
Class files are searched along the searchPath (see Smalltalk),
and any of binary-classFile, byteCode-classFile or sourceFile are loaded,
whichever is found first.
For binaries to be loaded, these must be found in a package-subdirectory
along the so called package path.
Sources in a package directory along the source path.
In practice, most Autoloaded classes are found and loaded as source file.

Initial Setup of Auoload Stubs:
At initial startup (i.e. when ST/X is NOT coming up with an image),
the 'patches' startup script recursively walks along all directories
below the TOP directory (that is one above the stx folder),
and installs autoload stubs for all .st class files found, for which no
corresponding class is already present.
As you can imagine, this takes a long time and makes the initial startup quite slow.
Therefore, this scheme is no longer the recommended one and we (at eXept)
always start ST/X with the '--quick' option, which skips this scan operation.
Late note:
    --quick is now (7.1.1) the default.
    To force an autoload scan, start stx with a --autoload argument.


Advantage of Autoload stubs:
Autoload stubs make it easier for a beginner to ST/X, to see what frameworks and classes
are there, as they appear in the browser with category and class name (although no
more details are initially visible.

[class variables:]

    LazyLoading             <Boolean>       if true, the loaded classes
                                            methods will NOT be compiled at
                                            autoload time, but instead when
                                            first called. This allows for a
                                            faster load. However, expect short
                                            pauses later when the methods are
                                            first executed.

    AutoloadFailedSignal    <Signal>        signal raised if an autoloaded
                                            classes source is not available.

    LoadedClasses           <Collection>    set of classes that heve been
                                            autoloaded (for later unload)

Related information:

    Smalltalk

Class protocol:

 autoloadFailedSignal

return the signal raised when an autoload fails

 addClass: aClassName

given a name, install a corresponding autoload class stub for it.
Return the (autoload-) stubClass or nil, if no new class was created.

usage example(s):

Autoload addClass:'Clock'

 addClass: aClassName inCategory: aCategory

given a name, install a corresponding autoload class stub for it.
Return the (autoload-) stubClass or nil, if no new class was created.

usage example(s):

Autoload addClass:'Clock' inCategory:'autoloaded-Demos'

 removeClass: aClass

remove a class from the list of loaded classes

 basicFileOutDefinitionOn: aStream withNameSpace: forceNameSpace withPackage: withPackage

print an expression to define myself on aStream.
Since autoloaded classes don't know their real definition, simply
output some comment string making things clear in the browser.

 initialize

initialize either the Autoload class
or load an autoloaded class and initialize it.

usage example(s):

initialize myself

 compileLazy

return the lazy loading flag - if on, fileIn is much faster,
but pauses are to be expected later, since methods are compiled
when first executed.

 compileLazy: aBoolean

turn on/off lazy loading - if on, fileIn is much faster,
but pauses are to be expected later, since methods are compiled
when first executed.
If you like it, add a line to your startup file.

 autoload

use this to force loading
- it is defined a noop in all non-autoloading classes.
Return the loaded class

usage example(s):

Class is already being loaded. In most cases we come here through the path: subclass autoload -> superclass autoload -> superclass initialize/postAutoload -> subclass autoload (hardcoded in initialize method). Simply ignore it here

usage example(s):

if filename is absolute, the autoload-class was created by an

usage example(s):

explicit install-as-autoloaded via the fileBrowser.

usage example(s):

reinstall the autoload class, this will be undone by #become:

usage example(s):

USER INFORMATION: this exception has been raised because an autoloaded class could not be loaded. Usually, this happens when the classes sourcefile is missing, unreadable or if an entry is missing in the abbreviation file. Check for a readable file named .st in the 'source' directory and (if the fileName is not the same as the class name) for a corresponding entry in the abbreviation file 'abbrev.stc'. Finally, your searchpath could be set wrong - the package might not be found along one of the directories named in systemPath. In the debugger, press 'Abort' to continue execution.

usage example(s):

autoloaded classes get their package from the revision (if present)

usage example(s):

this only happens with autoloaded sourceFiles which have no package

 at: arg

catch at: - redefined because it is understood

 basicNew

catch basicNew - load the class and send it to the real one

 basicNew: arg

catch basicNew: - load the class and send it to the real one

 classResources

catch classResources - load the class and resend to the real one

 comment

return the classes comment.
Autoloaded classes have no comment; but I myself have one

 copy

catch copy - load the class and resend #copy to the real one

 doesNotUnderstand: aMessage

caught a message; load the class and retry the message

 error

catch error - load the class and resend #error to the real one

 fromString: aString

catch - load the class and send it to the real one

 handle: handler do: aBlock

autoload the class and resend

 inspectorExtraAttributes
( an extension from the stx:libtool package )

extra (pseudo instvar) entries to be shown in an inspector.

 isAbstract

actually: don't know, but do not want to load my class for this query

 new

catch new - load the class and resend #new to the real one

 new: arg

catch new: - load the class and resend #new: to the real one

 privateClassesAt: aClassNameString

catch - load the class and send it to the real one

 readFrom: aStream

catch - load the class and send it to the real one

 readFrom: aStream onError: exceptionBlock

catch - load the class and send it to the real one

 readFromString: aString

catch - load the class and send it to the real one

 readFromString: aString onError: exceptionBlock

catch - load the class and send it to the real one

 respondsTo: aSelector

catch respondsTo: - load the class and resend #respondsTo: to the real one

 value

catch value - load the class and resend #value to the real one

 loadAndResendMessage

common helper to autoload a class and define a subclass of it by sending
the sender-message again.
This is invoked by all #subClass... definition messages.

 accepts: aSignalOrExceptionClass

redefined to avoid recursive autoload.
(#autoload eventually raises QueryExceptions.
These exception may send #accepts: to exception classes
that are currently being loaded)

 handles: anException

redefined to avoid recursive autoload.
(#autoload eventually raises QueryExceptions.
These exception may send #handles: to exception classes
that are currently being loaded)

 isBehavior

return true, if the receiver is describing another object's' behavior.
Autoloaded classes are definitely; therefore return true.

 isBeingLoaded

answer true if the class loading is currently in process

 isBuiltInClass

return true if this class is known by the run-time-system.
Returns false here.

 isLoaded

return true, if the class has been loaded.
Autoload itself is loaded, subclasses are not.
This allows testing whether a class has already been loaded.

 loadedClasses

return the set of classes that were autoloaded

 privateClassesOrAll: allOfThem

an autoloaded class has none

 wasAutoloaded: aClass

return true, if aClass was autoloaded

 withClass: aClass loadedDo: aBlock

ensure that aClass is loaded, while evaluating aBlock for it

usage example(s):

Autoload withClass:Array loadedDo:[:cls | self assert:cls isLoaded] Autoload withClass:Cons loadedDo:[:cls | self assert:cls isLoaded]

Subclasses (direct subclasses only):