swift bmi calculator

swift bmi calculator.playground

//: Playground - noun: a place where people can play

/*
The body mass index (BMI) is a measure used to quantify a person’s mass as well as interpret their body composition. It is defined as the mass (Kg) divided by height (m) squared.
 Here’s the BMI calculation formula:
 
 BMI = mass (kg) / height (m2) // Metre square
 
 If the BMI is greater than 25, use the print statement to tell the user that they are overweight.
 Otherwise, if the BMI is between 18.5 - 25, tell the user that they are of normal weight.
 Finally, if their BMI is below 18.5, tell the user that they are underweight.
 
---------------------------------- Difference Between Float & Double -------------------------------
 let floatingPointNumber : Float = 1.3 // max Float length after decimal can be 6
 
 let double : Double = 3.14159265359 // Double are 64 bit numbers.max Double length after decimal can be 15
----------------------------------------------------------------------------------------------------

*/

import UIKit

func calcBMI (mass : Double, height : Double) -> String{
    
    //let myBmi = mass / (height * height)
    
    let bmi = mass / pow(height, 2)
    
    //let shortenedBmi = round(bmi) // Not good. It is celing function & makes 29.7299 to 30.0
    
    let shortenedBmi = String(format: "%.2f", bmi) // It rounds to 2
    //let shortenedBmi = String(format: "%1.0f", bmi) // It rounds to 0
    //let shortenedBmi = String(format: "%1.1f", bmi) // It rounds to 1
    
    var interpretation = ""
    
    if bmi > 25{
        
        interpretation = "You are overweight mate."
    }
    //else if myBmi >= 18.5 && myBmi <= 25{
      else if bmi >= 18.5{
        interpretation = "You are healthy mate."
    }
    else
    {
        interpretation = "You are underweight mate."
    }
    
    //return "Your BMI is \(bmi). " + interpretation + " & BMI of a healthy guy is between 18.5 & 25"
    //return "Your BMI is " + String(bmi) + "." + interpretation + " & BMI of a healthy guy is between 18.5 & 25" // String(bmi) converts bmi data Type to String (Type Casting)
    return "Your BMI is \(shortenedBmi). \(interpretation) & BMI of a healthy guy is between 18.5 & 25"

}

print(calcBMI(mass: 90, height: 1.7399))

/*
-----------------------------BMI Calculate Imperial Units--------------------------------
 
 // 1 foot = 12 inches
 // 1 inch = 0.0254 meters
 // 1 pound = 0.45359237 kilograms
 
 // Example a person weighs 140 pounds & height is 5 ft 11 inches
-----------------------------------------------------------------------------------------
*/

func bmiCalcImperialUnits(weightInPounds : Double, heightInFeet: Double, remainderInches: Double) -> String
{
    
    let weightInKg = weightInPounds * 0.45359237
    
    let totalInches = (heightInFeet * 12) + remainderInches
    
    let heightInMeters = totalInches * 0.0254
    
    let bmi = weightInKg / pow(heightInMeters, 2)
    
    let shortenedBmi = String(format: "%.2f", bmi)

    
    return shortenedBmi
}


print(bmiCalcImperialUnits(weightInPounds: 140, heightInFeet: 5, remainderInches: 11))

Hi, I just randomly came across your gist and used it as an exercise to rewrite it using enums. I figured I might as well share it with you :).

import Cocoa

enum BodyComposition
{
    case overweight(bmi: Double)
    case healthy(bmi: Double)
    case underweight(bmi: Double)
}

extension BodyComposition
{
    init?(mass: Double, height: Double)
    {
        guard height > 0 && mass > 0 else {
            return nil
        }
        
        let bmi = mass / height * height
        
        switch bmi {
        case _ where bmi > 25:
            self = .overweight(bmi: bmi)
        case _ where bmi >= 18.5:
            self = .healthy(bmi: bmi)
        default:
            self = .underweight(bmi: bmi)
        }
    }
    
    init?(weightInPounds : Double, heightInFeet: Double, remainderInches: Double)
    {
        let weightInKg     = weightInPounds * 0.45359237
        let totalInches    = (heightInFeet * 12) + remainderInches
        let heightInMeters = totalInches * 0.0254
        
        self.init(mass: weightInKg, height: heightInMeters)
    }
}

//if let bodyComposition = BodyComposition(weightInPounds: 140, heightInFeet: 5, remainderInches: 11) {
if let bodyComposition = BodyComposition(mass: 90, height: 1.7399) {
    let out: (bmi: Double, interpretation: String)
    
    switch bodyComposition {
    case .overweight(let bmi):
        out = (bmi: bmi, interpretation: "You are overweight mate.")
    case .healthy(let bmi):
        out = (bmi: bmi, interpretation: "You are healthy mate.")
    case .underweight(let bmi):
        out = (bmi: bmi, interpretation: "You are underweight mate.")
    }
    
    print("Your BMI is \(String(format: "%1.0f", out.bmi)). \(out.interpretation) The BMI of a healthy guy is between 18.5 & 25")
}

Hi, I have made another method using your code according to my requirement. What it will do is, it will take the below input from user:
unit of weight (st/lbs OR kg/gram)
unit of height (ft/inches OR cm/mm)
and for every weight you will have to provide 2 input values, like feet and inches, kg and grams, stone and pounds, cm and mm.
if the user don't want to provide the input for the second value, then just provide 0.

func bmiCalcImperialUnits(weightBeforeDecimal : Double, weightAfterDecimal: Double, heightBeforeDecimal: Double, heightAfterDecimal: Double, heightUnit: String , weightUnit:String) -> String
{
    var weightInKg = 0.0

    var totalInches = 0.0

    var heightInMeters = 0.0

    if heightUnit == "cm" && weightUnit == "kg"
    {
        let cm = heightBeforeDecimal
        let mm = heightAfterDecimal
        let totalCMs = cm + (mm/10)
        
//        let feet = cm / 30.48
//        let inches = mm/25.4

        totalInches = totalCMs/2.54
        heightInMeters = totalInches * 0.0254
        
        let kg = weightBeforeDecimal
        let gram = weightAfterDecimal
        let totalKGs = kg + (gram / 1000)
        weightInKg = totalKGs
    }
    else if heightUnit == "cm" && weightUnit == "st/lbs"
    {
        let cm = heightBeforeDecimal
        let mm = heightAfterDecimal
        let totalCMs = cm + (mm/10)
        
//        let feet = cm / 30.48
//        let inches = mm/25.4

        totalInches = totalCMs/2.54
        heightInMeters = totalInches * 0.0254
        
        
        let stone = weightBeforeDecimal
        let pound = weightAfterDecimal
        let totalStones = stone + (pound / 14)
        weightInKg = totalStones *  6.35
    }
    else if heightUnit == "ft/inches" && weightUnit == "kg"
    {
        let heightInFeet = heightBeforeDecimal
        let remainderInches = heightAfterDecimal
        let totalInches = (heightInFeet * 12) + remainderInches
        heightInMeters = totalInches * 0.0254
        
        let kg = weightBeforeDecimal
        let gram = weightAfterDecimal
        let totalKGs = kg + (gram / 1000)
        weightInKg = totalKGs
    }
    else if heightUnit == "ft/inches" && weightUnit == "st/lbs"
    {
        let heightInFeet = heightBeforeDecimal
        let remainderInches = heightAfterDecimal
        let totalInches = (heightInFeet * 12) + remainderInches
        heightInMeters = totalInches * 0.0254
        
        let stone = weightBeforeDecimal
        let pound = weightAfterDecimal
        let totalStones = stone + (pound / 14)
        weightInKg = totalStones *  6.35
    }


    let bmi = weightInKg / pow(heightInMeters, 2)

    let shortenedBmi = String(format: "%.2f", bmi)


    return shortenedBmi
}

and how to call the method

print("BMI 1 cm            kg : \(bmiCalcImperialUnits(weightBeforeDecimal: 60, weightAfterDecimal: 999, heightBeforeDecimal: 100, heightAfterDecimal: 5, heightUnit: "cm", weightUnit: "kg"))")

print("BMI 2 cm        st/lbs : \(bmiCalcImperialUnits(weightBeforeDecimal: 5, weightAfterDecimal: 13, heightBeforeDecimal: 100, heightAfterDecimal: 5, heightUnit: "cm", weightUnit: "st/lbs"))")

print("BMI 3 ft/inches     kg : \(bmiCalcImperialUnits(weightBeforeDecimal: 60, weightAfterDecimal: 999, heightBeforeDecimal: 5, heightAfterDecimal: 11, heightUnit: "ft/inches", weightUnit: "kg"))")

print("BMI 4 ft/inches st/lbs : \(bmiCalcImperialUnits(weightBeforeDecimal: 5, weightAfterDecimal: 13, heightBeforeDecimal: 5, heightAfterDecimal: 11, heightUnit: "ft/inches", weightUnit: "st/lbs"))")