Using a string to switch between easings in ofxTween

Hi guys, im sure there is an easy way to do this but what i am wanting to do is use a string inside my ofxTween call to switch between the various easings that comes shipped with it.

The line below is what I am trying to manipulate.

  
ofxTween::map(float value, float inputMin, float inputMax, float outputMin, float outputMax, bool clamp, ofxEasing & easing, ofxEasingType type);  

the part that says ofxEasing & easing I would like to put a string variable in there so I can switch between the various easing functions with the below code.

  
    switch (key) {  
        case '1':  
            easeType = "easeLinear";  
            break;  
        case '2':  
            easeType = "easeQuad";  
            break;  
        case '3':  
            easeType = "easeCubic";  
            break;  
        case '4':  
            easeType = "easeQuart";  
            break;  
        case '5':  
            easeType = "easeQuint";  
            break;  
        case '6':  
            easeType = "easeExpo";  
            break;  
        case '7':  
            easeType = "easeSine";  
            break;  
        case '8':  
            easeType = "easeCirc";  
            break;  
        case '9':  
            easeType = "easeBack";  
            break;  
        case '0':  
            easeType = "easeBounce";  
            break;  
        case '-':  
            easeType = "easeElastic";  
            break;  
              
        default:  
            break;  
    }  

I know that the function in expecting a ofxEasing input and I am giving it a string but I was wondering how I would convert my string somehow so I could give it the correct input. Any ideas would be super appreciated.

Thanks.