Using pointer to action/method

2022-03-03T22:20:33.226000Z

I guess it is! Passing methods by address or using lambda expression (which is a nicer way to to something similar) also would be, if not rigorously speaking, at least from a modelling point of view. I am not a scholar, I have just been programming for decades in various languages, so there are concepts that are entirely clear in my mind for which I do not use the vocabulary from textbooks. I write code, not slides or presentations, the compiler/interpreter is my audience... :)

Using pointer to action/method

2022-03-03T21:50:48.263000Z

Isn't this called "dependancy injection"?

Using pointer to action/method

2022-03-03T20:20:06.371000Z

Although you cannot pass the address of a method and there are no lambda expressions in CODESYS, you can pass a pointer/reference of the outer function block to the inner function block, or pass the parent FB in the form of an instance of an interface the outer function block implements. Although it may not be your preferred idiom, I am not sure why you think it would not work.

Using pointer to action/method

2022-03-03T14:21:39.788000Z

"I came from Python where this things are daily basics" => ? AFAIK Python doesn't implement Interfaces. It only sports classes which implement methods/properties direct.

"sorry for asking something out of the codesys world" =>
Why are you sorry?

"What I was trying to do is a multiple uses block" => Please try to explain your question more thorough, if you can explain it well, we can surely help you find an anwser.

Besides that, I strongly advise against building a "multiple uses block" as it surely goes against the SOLID Single responsibility principle of ONE object should only do ONE task(!)

Using pointer to action/method

2022-03-03T14:05:09.397000Z

Ok, seeing your answers I think I can't do what I wanted to do.
I came from Python where this things are daily basics, sorry for asking something out of the codesys world.
Interfaces are good and I used it a lot, but it are meant to work with related objects, what I was trying to do is a multiple uses block, something that maybe I could post as a library. Thanks anyway!

Using pointer to action/method

2022-03-03T14:05:06.965000Z

Using pointer to action/method

2022-03-03T14:05:06.360000Z

Using pointer to action/method

2022-03-03T13:23:57.879000Z

1) "You can't pass a method or an action like that."
=> Obviously, but Interfaces are very neat and flexible and hold the key to solve this "problem". I simply explained what the basic mechanism of an interface is, rather then explain the correct usage in this specific case to solve the issue. I don't think that the user gains anything from Copy/Paste solutions if he/she does not understand the basics.

2) "Please inform yourself!"
=> A remark on which I will not comment 🙊

Using pointer to action/method

2022-03-03T12:25:49.122000Z

Whoho! If i get you right, it's still Object-oriented programming. Please inform yourself!

You can't pass a method or an action like that.

If the second fb owns the first fb, it will look like that:

FUNCTION_BLOCK SecondFB
VAR
    firstFb     : FirstFb;      // local instance of the child class
END_VAR

// call a method of the child
firstFb.SomethingCallable();

If the second fb doesn't know the first fb, you will need an interface.

FUNCTION_BLOCK FirstFb IMPLEMENTS I_FirstFb

FUNCTION_BLOCK SecondFB
VAR_INPUT
    ifirstFb    : I_FirstFb;    // reference to the first fb
END_VAR

// call a method of the reference
ifirstFb.SomethingCallable();

Using pointer to action/method

2022-03-03T11:49:38.527000Z

Interfaces are the way to go. Read up on it. It helps you do the following:

You can access any FB Instance's methods/properties, (BUT NO ACTIONS!) directly.

See Pseudo code below for a simple explanation (NO declarations provided!)

VAR
    FB1 : fbSomeFB; // Implements I_InterfaceExample;
    FB2 : fbSomeFB; // Implements I_InterfaceExample;
    xSwitch : BOOL;
    I_Example : I_InterfaceExample := FB1; // we staticly couple the interface to FB1 in the declaration

END_VAR

// BODY CODE

FB1.MethodX();

// Equals FB1.MethodX but after xSwitch points to FB2.MethodX
I_Example.MethodX();

IF xSwitch THEN
   // Now we dynamicly switch the Interface to FB2
   I_Example := FB2; // Please use __QueryInterface here since I skipped it for simplicity sake
   xSwitch := FALSE;
END_IF;

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