Validate that a calculation results in real numbers.

x = -2:2;
z = x.^exp(-x.^2);
mustBeReal(z)

Error using mustBeReal (line 13)
values must be real.

The value z is complex.

This class restricts the value of Prop1 to real values.

classdef MyClass
   properties
      Prop1 {mustBeReal}
   end
end

Create an object and assign a value to its property.

x = -2:0.1:2;
obj = MyClass;
obj.Prop1 = x.^exp(-x.^2);

Error setting 'Prop1' property of 'MyClass' class:
values must be real.

When you assign a value to the property, MATLAB calls mustBeReal with the value being assigned to the property. mustBeReal issues an error because the value assigned to Prop1 is complex.

function r = mbReal(z)
    arguments
        z (1,1) {mustBeReal}
    end
    r = randi(9,z);
end

Calling this function with a complex value results in an error being thrown by mustBeReal.

x = -1;
z = x.^exp(-x.^2);
r = mbReal(z);

Error using mbReal
Invalid input argument at position 1. Value must be real.