Need help inserting a string into a function

Question

I am looking to make repeated programming a little bit easier going forward. The program tells a motor to spin based on the manufacturers program guidelines. The current code will state:

motorname.spin(originallib::directionType::fwd, speed, originallib::velocityUnits::pct);

I want to be able to say:

int main()
{
run(LeftFront,80);
run(RightFront,80);
}

void run(string motorname, double speed )
{
motorname.spin(originallib::directionType::fwd, speed, originallib::velocityUnits::pct);
}

LeftFront and RightFront have been declared in a previous header file as

originallib::motor LeftFront=originallib::motor(originallib::PORT2,
                                                originallib::gearSetting::ratio18_1,
                                                true);

The issue I am running into is:

"error: no member named 'spin' in 'std::basic_string' "

Because the motorname.spin..... is part of the originallib

How can I go about achieving this?

`void run(string motorname, double speed )` tells the compiler that `motorname` is a `std::string`, not whatever class it's supposed to be. You want `void run(SomeClassHere motorname, double speed )` — user4581301, Aug 28 '18 at 20:40
Here is how they are defined in the header: `originallib::motor LeftFront=originallib::motor(originallib::PORT2,originallib::gearSetting::ratio18_1,true);` — Jason Becker, Aug 28 '18 at 21:04

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

void run(string motorname, double speed )

Tells the compiler that motorname is a std::string. std::string has no spin method. Based on

run(LeftFront,80);

where LeftFront is a originallib::motor, and assuming originallib::motor does indeed have a spin method, you really the function to look something like

void run(originallib::motor & motor, 
         double speed)
{
    motor.spin(originallib::directionType::fwd, 
               speed, 
               originallib::velocityUnits::pct);
}

so that a motor that can spin is provided instead of a string that can at best std::rotate

An alternative using names would be to have a map of string->motor key-value pairs that you can look up a motor name in the map and receive the mapped motor, on which you could invoke spin. This does not seem to be a desirable case here.

Sidenote:

You do not want to

originallib::motor LeftFront=originallib::motor(originallib::PORT2,
                                                originallib::gearSetting::ratio18_1,
                                                true);

in a header. This plays havoc on the One Definition Rule if multiple Translation Units include the header as each including translation unit will have its own, equally valid, LeftFront. Include guards will not prevent this because an include guard can only prevent a header from being included multiple times in one translation unit.

Need help inserting a string into a function

1 Answers1

Sidenote: