[CMake] Object Oriented Programming with CMake Script

[Tobias Becker]

For those interested: I have written a pure cmake module which allows
Object Oriented programming in CMake

you can download it through my blog at
http://thetoeb.wordpress.com/2014/02/25/object-oriented-cmake-next-iteration/

I also have a question:  Will CMake script ever support higher language
features like scoped function names, eval, dynamic functions, return values
(the workarounds for these features are costing me alot of performance)?


Here is an example of what you can do with the library:

function(test)
 ### using objects
 ### =============
# oo-cmake is very similar to javascript
# I actually used the javascript reference to figure out how things could
be done :)
 # oo-cmake is a pure object oriented language like javascript (only
objects no types per se)
# oo-cmake is currently file based and relies heavily on dynamic functions
so to be upfront about it:
 # oo-cmake is very slow (depending on what your doing)

## creating a object
## =================
 obj_new(myobject)
# ${myobject} now is a reference to an object
obj_exists(${myobject} _exists)
 assert(_exists)

## deleting a object
## =================
 # oo-cmake does not contains automatic memory management
# you can however remove all objects by calling obj_cleanup
 # (a very crude way of garbage collection) I would suggest calling it at
the end of cmake.
obj_new(object_to_delete)
 obj_delete(${object_to_delete})
# object_to_delete still contains the same reference
# but the object does not exists anymore and the following returns false
 obj_exists(${object_to_delete} _exists)
assert(NOT _exists)


## setting and setting property
 ## ==================
obj_new(myobject)
# call obj_set passing the object reference
 # the propertyname 'key1' and the value 'val1'
# everything beyond 'key1' is saved (as a list)
 obj_set(${myobject} key1 "val1")
#call obj_get passing the object refernce the result variable and
 # the key which is to be gotten
obj_get(${myobject} theValue key1)
assert(theValue)
 assert(${theValue} STREQUAL "val1")


## setting a function and calling it
 ## =================================
obj_new(obj)
obj_set(${obj} last_name "Becker")
 obj_set(${obj} first_name "Tobias")
#obj_setfunction accepts any function (cmake command, string function, file
function, unique function (see function tutorial))
 # if you use a cmake function be sure that it will not be overwritten
# the safest way to add a function is to use obj_declarefunction
 # you can either specify the key where it is to be stored or not
# if you do not specify it the name of the function is used
 function(greet result)
# in the function you have read access to all fields of the proeprty
# as will as to 'this' which contains the reference to the object

# this sets the variable ${result} in PARENT_SCOPE (returning values in
cmake)
set(${result} "Hello ${first_name} ${last_name}!" PARENT_SCOPE)

endfunction()
obj_setfunction(${obj} greet)
obj_callmember(${obj} greet res)
 assert(res)
assert(${res} STREQUAL "Hello Tobias Becker!")
# alternatively you can also use obj_declarefunction
 # this is actually the easiest way to define a function in code
obj_declarefunction(${obj} say_goodbye)
 function(${say_goodbye} result)
set(${result} "Goodbye ${first_name} ${last_name}!" PARENT_SCOPE)
 endfunction()
obj_callmember(${obj} say_goodbye res)
assert(res)
 assert(res STREQUAL "Goodbye Tobias Becker!")

## built in methods
## ================
 # obj_new creates a object which automatically inherits Object
# Object contains some functions e.g. to_string, print, ...
 #
obj_new(obj)
obj_callmember(${obj} print)

# this prints all members
# ie
#{
# print: [function],
 # to_string: [function],
# __ctor__: [object :object_Y3dVWkChKi],
# __proto__: [object :object_AztQwnKoE7],
 #}


## constructors
## ============
 # you can easily define a object type via constructor
function(MyObject)
# declare a function on the prototype (which is accessible for all objects)
 # inheriting from MyObject
obj_declarefunction(${__proto__} myMethod)
function(${myMethod} result)
 set(${result} "myMethod: ${myValue}" PARENT_SCOPE)
this_set(myNewProperty "this is a text ${myValue}")
 endfunction()

# set a field for the object
this_set(myValue "hello")
 endfunction()

obj_new(obj MyObject)
# type of object will now be MyObject
 obj_gettype(${obj} type)
assert(type)
assert(${type} STREQUAL MyObject)
 # call
obj_callmember(${obj} myMethod res)
assert(res)
 assert(${res} STREQUAL "myMethod: hello")
obj_set(${obj} myValue "othervalue")
obj_callmember(${obj} myMethod res)
 assert(res)
assert(${res} STREQUAL "myMethod: othervalue")
obj_get(${obj} res myNewProperty)
 assert(res)
assert(${res} STREQUAL "this is a text othervalue")

## functors
 ## ========

## binding a function
## ==================
 # you can bind any function to an object without
# setting it as property
# causing the function to get access to 'this'
 # and all defined properties
function(anyfunction)
this_callmember(print)
 endfunction()
obj_new(obj)
obj_bindcall(${obj} anyfunction)
 ## print the object
# alternatively you can bind the function to the object
obj_bind(boundfu ${obj} anyfunction)
 call_function(${boundfu})
# prints the object
# alternatively you can bind and import then function
 # beware that you might overwrite a defined function if you append REDEFINE
#
obj_bindimport(${obj} anyfunction myBoundFunc REDEFINE)
 myBoundFunc()
# print the object



## extended a 'type'
 ## =================

endfunction()
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