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Redeclaration


By using the keyword redeclare it is possible to modify the type and/or the prefixes and possibly the dimension sizes of a declared element. This kind of modification is called a redeclaration. In most cases a declaration that can be redeclared must include the prefix replaceable.

The element in a redeclaration must have a type that is either a subtype of the replaceable element in the modified class or a subtype of a constraining type. An example is shown below with the concepts of redeclaration.


1 Connector Classes

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type Voltage = Real(unit = "V");
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​

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type Current = Real(unit = "A");
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​

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connector Pin
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  Voltage     v;
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  flow Current   i;
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end Pin;
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​

2 Resistor and TempResistor

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model Resistor
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  Pin       p, n                "Positive and Negative Pins";
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  Voltage     v;
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  Current     i;
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  parameter Real R(unit = "Ohm")          "Resistance";
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equation
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  v = R*i;
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end Resistor;
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​

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model TempResistor                  "Temperature dependent Resistor"
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  Pin       p, n                "Positive and Negative Pins";
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  Voltage     v;
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  Current     i;
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  parameter Real R(unit = "Ohm")          "Resistance at reference Temperature";
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  parameter Real RT(unit = "Ohm/degC")   = 0     "Temperature dependent Resistance";
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  parameter Real Tref(unit = "degC")   = 20    "Reference Temperature";
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  Real        Temp           = 20    "Actual Temperature";
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equation
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  v = i*(R + RT*(Temp - Tref));
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end TempResistor;
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​

3 MiniCircuit

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class MiniCircuit
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  replaceable discrete Resistor R1;
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end MiniCircuit;
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​


The redeclaration of the R1 element changes its type from Resistor to TempResistor and its prefix from discrete to parameter.


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class MiniCircuitRed
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  MiniCircuit tempcircuit(redeclare parameter TempResistor R1);
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end MiniCircuitRed;
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​


The MiniCircuitRed class can be rewritten as the MiniCircuit2


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class MiniCircuit2
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  parameter TempResistor R1;
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end MiniCircuit2;
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​

4 Redeclaration with Extends Clause

The next example illustrates a redeclaration used in an extends clause.


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class RedA
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  parameter Real x;
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end RedA;
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​

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class RedA2                    // A2 is a subtype of A
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  parameter Real x = 3.14;
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  parameter Real y;
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end RedA2;
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​

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class RedB
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  replaceable RedA a(x = 1);
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end RedB;
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​


The redeclaration redeclare RedA2 a(y=2) is used in an extends clause to replace the original declaration RedA a(x=1) from class RedB, but merging the original nested modifier (x=1) with the modifiers in the redeclaration to effectively get RedA2 a(x=1,y=2). The type of the redeclared field a in class RedB is changed from RedA to RedA2 in class RedB2 which is correct since RedA2 is a subtype of RedA.


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class RedB2
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  extends RedB(redeclare RedA2 a(y = 2));    // The result after redeclaration is RedA2 a(x = 1, y = 2)
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end RedB2;
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​


The class RedB, is equivalent to the class B2expanded below.


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class B2expanded
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  RedA2 a(x = 1, y = 2);
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end B2expanded;
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​

4.1 Flattening RedB, B2expanded

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instantiateModel(RedB2)
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​

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instantiateModel(B2expanded)
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​