else if executes executes automatically before asking for user input - c++

Question

I am new to c++ programming, I would like to create a program to find area, volume of shapes I used switch case to select shapes and used else if inside switch for selecting area or volume but it executes only one switch statement.
#include <iostream>
#include<cmath>
#define _USE_MATH_DEFINES
#include<math.h>
#define PI 3.14159
using namespace std;
int main() {
double radius;
double square;
double qube;
double quboid;
double cylinder;
double sphere;
double a;
double length;
double breadth;
double height;
double width;
char userchoice1;
char userchoice;
cout << "Select any shape by typing the no correctly\n";
cout << "1-square\n";
cout << "2-Cube\n";
cout << "3-Cuboid\n";
cout << "4-Circle\n";
cout << "5-Sphere\n";
cout << "6-rectangle\n";
cout << "Select any shape by typing the no correctly\n";
cin >> userchoice;
switch (userchoice) {
case '1':
cout << "3-area\n";
cout << "4-perimeter\n";
if (userchoice = 3) {
cout << "Enter side a\n";
cin >> a;
cout << "Area of square is " << a * a << "sq.units" << endl;
} else if (userchoice = 4) {
cout << "Enter side\n";
cin >> a;
cout << "Perimeter of square is " << 4 * a << "sq.units" << endl;
}
break;
case '2':
cout << "1-area\n";
cout << "2-volume\n";
if (userchoice = 1) {
cout << "Enter side a\n";
cin >> a;
cout << "Area of cube is " << 6 * a * a << "sq.units" << endl;
} else if (userchoice = 2) {
cout << "Enter side a\n";
cin >> a;
cout << "Volume of cube is " << a * a * a << "cu.units" << endl;
}
break;
case '3':
cout << "Enter length, breadth, height\n";
cin >> breadth;
cin >> length;
cin >> height;
cout << "Area of cuboid is " << (length * breadth * height) << "sq.units" << endl;
break;
case '4':
cout << "1-circumference\n";
cout << "2-Area\n";
if (userchoice = 1) {
cout << "Enter the radius of circle\n";
cin >> radius;
cout << "Circumference of circle is " << 2 * PI * radius << endl;
} else if (userchoice = 2) {
cout << "Enter the radius of circle\n";
cin >> radius;
cout << "Area of circle is " << PI * radius * radius << "sq.units" << endl;
}
break;
case '5':
cout << "1-Area\n";
cout << "2-volume\n";
if (userchoice = 1) {
cout << "Enter the radius of Sphere\n";
cin >> radius;
cout << "Area of Sphere is " << 4 * PI * radius * radius << "sq.units" << endl;
} else if (userchoice = 2) {
cout << "Enter the radius of Sphere\n";
cin >> radius;
cout << "Volume of Sphere is " << (4 / 3 * PI * radius * radius) << "cu.units" << endl;
}
break;
case '6':
cout << "1-Area\n";
cout << "2-perimeter\n";
if (userchoice = 1) {
cout << "Enter length width\n";
cin >> length;
cin >> width;
cout << "Area of rectangle: " << length * width << "sq.units" << endl;
} else if (userchoice = 2) {
cout << "Enter side\n";
cin >> a;
cout << "Perimeter of rectangle is " << 4 * a << "sq.units" << endl;
}
break;
}
}

Answer 1

switch statements can only execute through one case. It can "fall through" if you don't use breaks though. If you mean that it's not executing any of the if statements in the switch statement, it's because you're using the "assignment" operator (=) in the condition. You should be using the "is equal to" operator (==) instead.
So your if statements should be something like this:
if (userchoice == 1) {
// ... do something ...
}
else if (userchoice == 2) {
// ... do something else ...
}
Even if you do that, you have another problem that I notice. You're using the same variable in the condition of the if and switch statements. Doing it that way will make it impossible to execute some routes. You should use separate variables for both and prompt the user for both. Either that, or reassign "userchoice" to be used in the if statements.
Also, you're declaring "userchoice" as a char. If you declare it as a char, you should test for a char in the conditions. If not, declare it as an int.