Propeller Manual

OBJ – Spin Language Reference
Page 142 · Propeller Manual v1.1
Method reference symbol (a period ‘.’) and finally the name of the method to call.
Num.ToStr, for instance, calls the Numbers object’s public ToStr method. Term.Str calls the
TV_Terminal’s public Str method. In this case the Num.ToStr has two parameters, in
parentheses, and
Term.Str has one parameter.
Also notice that the second parameter of the
Num.ToStr call is Num#DEC. The # symbol is the
Object-Constant reference symbol; it gives access to an object’s constants. In this case,
Num#DEC refers to the DEC (decimal format) constant in the Numbers object.
See Object-Method Reference ‘
.’ and Object-Constant Reference ‘#’> in Table 2-16:
Symbols on page 207 for more information.
Multiple instances of an object can be declared with the same object symbol using array
syntax and can be accessed similar to arrays as well. For example:
OBJ
PWM[2] : "PWM"
PUB GenPWM
PWM[0].Start
PWM[1].Start
This example declares PWM as an array of two objects (two instances of the same object). The
object itself just happens to be called “
PWM” as well. The public method, GenPWM, calls the
Start method of each instance using indexes 0 and 1 with the object symbol array, PWM.
Both instances of the
PWM object are compiled into the application such that there is one copy
of its program code (
PUBs, PRIs, and DATs) and two copies of its variable blocks (T VARs). This
is because, for each instance, the code is the same but each instance needs its own variable
space so it can operate independent of the other.
An important point to consider with multiple instances of an object is that there is only one
copy of its
DAT block because it may contain Propeller Assembly code. DAT blocks can also
contain initialized data and regions set aside for workspace purposes, all with symbolic
names. Since there is only one copy of it for multiple instances of an object, that area is
shared among all instances. This provides a convenient way to create shared memory
between multiple instances of a particular object.
Scope of Object Symbols
Object symbols defined in Object Blocks are global to the object in which they are defined
but are not available outside of that object. This means that these object symbols can be
accessed directly from anywhere within the object but their name will not conflict with
symbols defined in other parent or child objects.