Global variable and class

testcalss.m

    classdef testcalss

        properties(Access = public)
            a;
            F;
        end

        methods(Access = public)
            function this = testcalss()            
                if (1 == 1)
                    this.F = eval('@(x)a * x');
                    eval('this.a = 5');
                end
            end

            function Calculate(this)
                a = this.a;
                this.F(1);
            end
        end
    end

test.m:

    global solver;
    solver = testcalss();
    solver.Calculate();

I execute test and after it I get such message:

    Undefined function or variable 'a'.

    Error in testcalss/testcalss/@(x)a*x

    Error in testcalss/Calculate (line 18)
                this.F(1);

    Error in test1 (line 3)
    solver.Calculate();

Where is my bug?

Answer 1

[hedgehogues]

http://stackoverflow.com/questions/33942216/passing-anonymous-function-to-method

I found the solve. You can see my account on the stackoverflow.

Answer 2

[Adam]

The definition

this.F = eval('@(x)a * x');

has no idea what 'a' is, it has not been defined in this scope.

Using eval is a very bad idea in general, but that is a side issue other than that I have deliberately never taken the time to understand fully how it works.

this.F = eval('@(x) this.a * x');

would be syntactically fine so far as I can see, but then you try to eval the setting of a immediately afterwards. this.a would need to be set before the above call, but why do you need eval for that. Just use

this.a = 5;

followed by either

this.F = @(this,x) this.a * x

or

this.F = @(a,x) a * x

and pass in this.a as an argument when you call it, though it isn't at all obvious why you would want such a setup rather than just a standard function on your class that use the class property 'a'.