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

type Voltage = Real(unit = "V");
type Current = Real(unit = "A");
connector Pin Voltage v; flow Current i; end Pin;

2 Resistor and TempResistor

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

3 MiniCircuit

class MiniCircuit replaceable discrete Resistor R1; end MiniCircuit;

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

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

The MiniCircuitRed class can be rewritten as the MiniCircuit2

class MiniCircuit2 parameter TempResistor R1; end MiniCircuit2;

4 Redeclaration with Extends Clause

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

class RedA parameter Real x; end RedA;
class RedA2 // A2 is a subtype of A parameter Real x = 3.14; parameter Real y; end RedA2;
class RedB replaceable RedA a(x = 1); end RedB;

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.

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

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

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

4.1 Flattening RedB, B2expanded

instantiateModel(RedB2)
instantiateModel(B2expanded)