Drawing Views, violating the open/closed principle.

old-days.m

#import <stdio.h>

// clang -g -Wall -o old-days old-days.m

typedef struct Rect {
    int x, y, w, h;
} Rect;


typedef enum {
    kButtonView,
    kSliderView,
    kPonyView
} ViewKind;

typedef struct View {
    ViewKind kind;
    Rect   bounds;
} View;


static void ButtonDraw (View *view) {}
static void SliderDraw (View *view) {}
static void PonyDraw (View *view) {}

void DrawViews (View *views[], int count) {

    for (int i = 0; i < count; i++) {
        View *view = views[i];
        switch (view->kind) {
        case kButtonView:
            printf ("Drawing a button!\n");
            ButtonDraw (view);
            break;
        case kSliderView:
            printf ("Drawing a slider!\n");
            SliderDraw (view);
            break;
        case kPonyView:
            printf ("OMG PONIES!\n");
            PonyDraw (view);
            break;
        }
    }

} // DrawViews


int main (void) {
    View viewsObjects[3] = { { .kind = kButtonView }, 
                             { .kind = kSliderView },
                             { .kind =  kPonyView } };

    View *viewsToDraw[] = { &viewsObjects[0], &viewsObjects[1], &viewsObjects[2] };
    DrawViews (viewsToDraw, sizeof(viewsToDraw) / sizeof(*viewsToDraw));

    return 0;

} // main