clay - A minimalist framework for large scale OO Projects
Clay introduces a method ensemble to both oo::class and oo::object called clay. This ensemble handles all of the high level interactions within the framework. Clay stores structured data. Clan manages method delegation. Clay has facilities to manage the complex interactions that come about with mixins.
The central concept is that inside of every object and class (which are actually objects too) is a dict called clay. What is stored in that dict is left to the imagination. But because this dict is exposed via a public method, we can share structured data between object, classes, and mixins.
Clay uses a standardized set of method interactions and introspection that TclOO already provides to perform on-the-fly searches. On-the-fly searches mean that the data is never stale, and we avoid many of the sorts of collisions that would arise when objects start mixing in other classes during operation.
The clay methods for both classes and objects have a get and a set method. For objects, get will search through the local clay dict. If the requested leaf is not found, or the query is for a branch, the system will then begin to poll the clay methods of all of the class that implements the object, all of that classes’ ancestors, as well as all of the classes that have been mixed into this object, and all of their ancestors.
Intended branches on a tree end with a directory slash (/). Intended leaves are left unadorned. This is a guide for the tool that builds the search results to know what parts of a dict are intended to be branches and which are intended to be leaves. For simple cases, branch marking can be ignored:
::oo::class create ::foo { }
::foo clay set property/ color blue
::foo clay set property/ shape round
set A [::foo new]
$A clay get property/
{color blue shape round}
$A clay set property/ shape square
$A clay get property/
{color blue shape square}
But when you start storing blocks of text, guessing what field is a dict and what isn’t gets messy:
::foo clay set description {A generic thing of designated color and shape}
$A clay get description
{A generic thing of designated color and shape}
Without a convention for discerning branches for leaves what should have been a value can be accidentally parsed as a dictionary, and merged with all of the other values that were never intended to be merge. Here is an example of it all going wrong:
::oo::class create ::foo { }
# Add description as a leaf
::foo clay set description {A generic thing of designated color and shape}
# Add description as a branch
::foo clay set description/ {A generic thing of designated color and shape}
::oo::class create ::bar {
superclass foo
}
# Add description as a leaf
::bar clay set description {A drinking establishment of designated color and shape and size}
# Add description as a branch
::bar clay set description/ {A drinking establishment of designated color and shape and size}
set B [::bar new]
# As a leaf we get the value verbatim from he nearest ancestor
$B clay get description
{A drinking establishment of designated color and shape and size}
# As a branch we get a recursive merge
$B clay get description/
{A drinking establishment of designated color and size thing of}
Clay is built using the oo::dialect module from Tcllib. oo::dialect allows you to either add keywords directly to clay, or to create your own metaclass and keyword set using Clay as a foundation. For details on the keywords and what they do, consult the functions in the ::clay::define namespace.
Method Delegation It is sometimes useful to have an external object that can be invoked as if it were a method of the object. Clay provides a delegate ensemble method to perform that delegation, as well as introspect which methods are delegated in that manner. All delegated methods are marked with html-like tag markings (< >) around them.
::clay::define counter {
Variable counter 0
method incr {{howmuch 1}} {
my variable counter
incr counter $howmuch
}
method value {} {
my variable counter
return $counter
}
method reset {} {
my variable counter
set counter 0
}
}
::clay::define example {
variable buffer
constructor {} {
# Build a counter object
set obj [namespace current]::counter
::counter create $obj
# Delegate the counter
my delegate <counter> $obj
}
method line {text} {
my <counter> incr
append buffer $text
}
}
set A [example new]
$A line {Who’s line is it anyway?}
$A <counter> value
1
Because many features in this package may be added as commands to future tcl cores, or be provided in binary form by packages, I need a declaritive way of saying Create this command if there isn't one already. The ninja argument is a script to execute if the command is created by this mechanism.
Perform a noop. Useful in prototyping for commenting out blocks of code without actually having to comment them out. It also makes a handy default for method delegation if a delegate has not been assigned yet.
Process the queue of objects to be destroyed
Mark an objects for destruction on the next cleanup
Append a line of text to a variable. Optionally apply a string mapping.
Convert a string representation of a uuid into its binary format.
Compare two uuids for equality.
uuid generate -> string rep of a new uuid uuid equal uuid1 uuid2
Output a dictionary removing any . entries added by clay::tree::merge
Helper function for ::clay::tree::sanitize Formats the string representation for a dictionary element within a human readable stream of lines, and determines if it needs to call itself with further indentation to express a sub-branch
Return the path as a storage path for clay::tree with all branch terminators removed. This command will also break arguments up if they contain /.
Example:
> clay::tree::storage {foo bar baz bang}
foo bar baz bang
> clay::tree::storage {foo bar baz bang/}
foo bar baz bang
> clay::tree::storage {foo bar baz bang:}
foo bar baz bang:
> clay::tree::storage {foo/bar/baz bang:}
foo bar baz bang:
> clay::tree::storage {foo/bar/baz/bang}
foo bar baz bang
Set an element with a recursive dictionary, marking all branches on the way down to the final element. If the value does not exists in the nested dictionary it is added as a leaf. If the value already exists as a branch the value given is merged if the value is a valid dict. If the incoming value is not a valid dict, the value overrides the value stored, and the value is treated as a leaf from then on.
Example:
> set r {}
> ::clay::tree::dictset r option color default Green
. {} option {. {} color {. {} default Green}}
> ::clay::tree::dictset r option {Something not dictlike}
. {} option {Something not dictlike}
# Note that if the value is not a dict, and you try to force it to be
# an error with be thrown on the merge
> ::clay::tree::dictset r option color default Blue
missing value to go with key
A recursive form of dict merge, intended for modifying variables in place.
Example:
> set mydict {sub/ {sub/ {description {a block of text}}}}
> ::clay::tree::dictmerge mydict {sub/ {sub/ {field {another block of text}}}}]
> clay::tree::print $mydict
sub/ {
sub/ {
description {a block of text}
field {another block of text}
}
}
A recursive form of dict merge
A routine to recursively dig through dicts and merge adapted from http://stevehavelka.com/tcl-dict-operation-nested-merge/
Example:
> set mydict {sub/ {sub/ {description {a block of text}}}}
> set odict [clay::tree::merge $mydict {sub/ {sub/ {field {another block of text}}}}]
> clay::tree::print $odict
sub/ {
sub/ {
description {a block of text}
field {another block of text}
}
}
Named Procedures as new command
This proc will generate a namespace, a "mother of all classes", and a rudimentary set of policies for this dialect.
Support commands; not intended to be called directly.
Implementation of the languages' define command
New OO Keywords for clay
An annotation that objects of this class interact with delegated methods. The annotation is intended to be a dictionary, and the only reserved key is description, a human readable description.
Specify the a method for the class object itself, instead of for objects of the class
And alias to the new Class_Method keyword
Define an option for the class
Define a class of options All field / value pairs will be be inherited by an option that specify name as it class field.
This keyword can also be expressed:
property variable NAME {default DEFAULT}
Variables registered in the variable property are also initialized (if missing) when the object changes class via the morph method.
Produce the body of an ensemble's public dispatch method ensemble is the name of the the ensemble. einfo is a dictionary of methods for the ensemble, and each value is a script to execute on dispatch
Example:
::clay::ensemble_methodbody foo {
bar {tailcall my Foo_bar {*}$args}
baz {tailcall my Foo_baz {*}$args}
clock {return [clock seconds]}
default {puts "You gave me $method"}
}
Cancel a scheduled event
Generate an event Adds a subscription mechanism for objects to see who has recieved this event and prevent spamming or infinite recursion
Called recursively to produce a list of who recieves notifications
Final delivery to intended recipient object
Evaluate an event script in the global namespace
Schedule an event to occur later
Subscribe an object to an event pattern
Unsubscribe an object from an event pattern
An object which is intended to be it's own class.
Methods
Return this class and all ancestors in search order.
Return a complete dump of this object's clay data, but only this object's clay data.
Pull a chunk of data from the clay system. If the last element of path is a branch, returns a recursive merge of all data from this object and it's constituent classes of the data in that branch. If the last element is a leaf, search this object for a matching leaf, or search all constituent classes for a matching leaf and return the first value found. If no value is found, returns an empty string. If a branch is returned the topmost . entry is omitted.
Pull a chunk of data from the class's clay system. If no value is found, returns an empty string. If a branch is returned the topmost . entry is omitted.
Pull a chunk of data from the class's clay system. If no value is found, returns an empty string.
Recursively merge the dictionaries given into the object's local clay storage.
Replace the contents of the internal clay storage with the dictionary given.
Return the first matching value for the path in either this class's clay data or one of its ancestors
Merge the conents of value with the object's clay storage at path.
clay::object This class is inherited by all classes that have options.
Methods
Return the class this object belongs to, all classes mixed into this object, and all ancestors of those classes in search order.
Store VALUE in such a way that request in SEARCH for PATH will always return it until the cache is flushed
Pull a value from either the object's clay structure or one of its constituent classes that matches the field name. The order of search us:
1. The as a value in local dict variable config
2. The as a value in local dict variable clay
3. As a leaf in any ancestor as a root of the clay tree
4. As a leaf in any ancestor as const field
5. As a leaf in any ancestor as option field default
Introspect or control method delegation. With no arguments, the method will return a key/value list of stubs and objects. With just the stub argument, the method will return the object (if any) attached to the stub. With a stub and an object this command will forward all calls to the method stub to the object.
Return a complete dump of this object's clay data, as well as the data from all constituent classes recursively blended in.
Return a dictionary describing the method ensembles to be assembled for this object
Evaluated a script in the namespace of this object
Trigger the InitializePublic private method
Returns 1 if path exists in either the object's clay data. Values greater than one indicate the element exists in one of the object's constituent classes. A value of zero indicates the path could not be found.
Wipe any caches built by the clay implementation
A convenience wrapper for
oo::objdefine [self] forward {*}$args
Pull a chunk of data from the clay system. If the last element of path is a branch (ends in a slash /), returns a recursive merge of all data from this object and it's constituent classes of the data in that branch. If the last element is a leaf, search this object for a matching leaf, or search all constituent classes for a matching leaf and return the first value found. If no value is found, returns an empty string.
A modified get which is tailored to pull only leaf elements
Recursively merge the dictionaries given into the object's local clay storage.
Perform [oo::objdefine [self] mixin] on this object, with a few additional rules: Prior to the call, for any class was previously mixed in, but not in the new result, execute the script registered to mixin/ unmap-script (if given.) For all new classes, that were not present prior to this call, after the native TclOO mixin is invoked, execute the script registered to mixin/ map-script (if given.) Fall all classes that are now present and “mixed in”, execute the script registered to mixin/ react-script (if given.)
With no arguments returns the map of stubs and classes mixed into the current object. When only stub is given, returns the classes mixed in on that stub. When stub and classlist given, replace the classes currently on that stub with the given classes and invoke clay mixin on the new matrix of mixed in classes.
Return either self if that path exists in the current object, or return the first class (if any) along the clay search path which contains that element.
Replace the contents of the internal clay storage with the dictionary given.
Return true, and set valuevar to the value and isleafar to true for false if PATH was found in the cache.
Source the given filename within the object's namespace
Merge the conents of value with the object's clay storage at path.
Instantiate variables. Called on object creation and during clay mixin.
Sean Woods mailto:<yoda@etoyoc.com>
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Copyright © 2018 Sean Woods <yoda@etoyoc.com>