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twinControls · 2022-10-10T12:26:25Z

The fluent interface design pattern makes your code more readable and simple. We can think of the Fluent Interface as a concept, whereas the method chaining is an implementation. The goal of the fluent interface design is to be able to apply multiple properties to an object by connecting the methods with dots(.) instead of having to apply to each method individually. Let's say you want to initialize an axis by setting some of its properties and methods. You can achieve this using one line of code as below: fbInitAxis.Name('Conveyor_1') .Enable(TRUE) .HomePosition(0) .Speed(10) .Accel(20) .Decel(15) .BelongsTo('Gantry_1'); By making the code understandable and fluid, the fluent interface gives you the impression that you are reading a sentence. To achieve this design pattern, you would need to use method chaining. In this technique, each method returns an object and you can chain all the methods together. Let's assume we need a function block that can implement multiple math operations. To demonstrate the fluent interface and method chaining, first we will create an interface called I_Calculate and we will set the return type of each method to this interface. METHOD SetNumber : I_Calculate VAR_INPUT lNumber : LREAL; END_VAR METHOD IncreaseBy : I_Calculate VAR_INPUT lIncreaseBy : REAL; END_VAR METHOD DecreaseBy : I_Calculate VAR_INPUT lDecreaseBy : REAL; END_VAR METHOD MultiplyBy : I_Calculate VAR_INPUT lMultiplyBy : REAL; END_VAR METHOD DivideBy : I_Calculate VAR_INPUT lDivideBy : REAL; END_VAR METHOD GetResult : LREAL METHOD Clear : I_Calculate As you can see above, each math operation method is set to return the I_Calculate interface. Now we will create a function block called FB_Calculate which will implement the I_Calculate interface. FB_Calculate: FUNCTION_BLOCK FB_Calculate IMPLEMENTS I_Calculate VAR_INPUT END_VAR VAR_OUTPUT END_VAR VAR {attribute 'hide'} lResult : LREAL := 0; END_VAR Method SetNumber: METHOD SetNumber : I_Calculate VAR_INPUT lNumber : LREAL; END_VAR lResult := lNumber; SetNumber := THIS^; Method IncreaseBy: METHOD IncreaseBy : I_Calculate VAR_INPUT lIncreaseBy : REAL; END_VAR lResult := lResult + lIncreaseBy; IncreaseBy := THIS^; Method DecreaseBy: METHOD DecreaseBy : I_Calculate VAR_INPUT lDecreaseBy : REAL; END_VAR lResult := lResult - lDecreaseBy; DecreaseBy := THIS^; Method MultiplyBy: METHOD MultiplyBy : I_Calculate VAR_INPUT lMultiplyBy : REAL; END_VAR lResult := lResult * lMultiplyBy; MultiplyBy := THIS^; Method DivideBy: METHOD DivideBy : I_Calculate VAR_INPUT lDivideBy : REAL; END_VAR lResult := lResult / lDivideBy; DivideBy := THIS^; Method GetResult: METHOD GetResult : LREAL GetResult := lResult; Method Clear: METHOD Clear : I_Calculate MEMSET(destAddr:= ADR(lResult),fillByte :=0, n:=SIZEOF(lResult)); Clear := THIS^; In the MAIN program; PROGRAM MAIN VAR fMyResult : LREAL; fbCalculate : FB_Calculate; END_VAR fMyResult := fbCalculate.Clear() .SetNumber(12) .DecreaseBy(2) .IncreaseBy(3.9) .MultiplyBy(5) .DivideBy(3) .GetResult(); Everyone even non-programmers can easily grasp the code thanks to the fluent interface and method chaining.

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Fluent Interface and Method Chaining in TwinCAT 3

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Last Post by runtimevictor 3 years ago

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CodeX

Feb 12, 2023 3:38 am

(@codex)

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Hi @ddsouza1, just remove the _ from the last statement and you should be good go.

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