Convert with Measurement SwiftUI

Question

Created Dec ’20

Replies 1

Boosts 0

Views 1.1k

Participants 2

Hello
I'm using Measurement(...) to convert watts to femtowatts, but if I convert 1 watts to femtowatts I get 999999999999999.9 instead of 1e+15, I have no idea on how to fix it, any help or ideas, here is the code
:

Code Block import SwiftUI
struct PowerView: View {
    
    @State private var inputValue = ""
    
     let inputUnits = [
        "watts",
        "femtowatts"
    ]
    let outputUnits = [
        "watts",
        "femtowatts"
   ]
    @State private var inputUnitValue = 0
    
    @State private var outputUnitValue = 1
    
    var after: String{
        var input = Measurement(value: 0, unit: UnitPower.watts)
        var output: String = ""
        
        switch inputUnits[inputUnitValue] {
        case "watts": input = Measurement(value: Double(inputValue) ?? 0, unit: UnitPower.watts)
        case "femtowatts": input = Measurement(value: Double(inputValue) ?? 0, unit: UnitPower.femtowatts)
        default: input = Measurement(value: Double(inputValue) ?? 0, unit: UnitPower.watts)
        }
        switch outputUnits[outputUnitValue] {
        case "watts": output = String(describing: input.converted(to: UnitPower.watts))
        case "femtowatts": output = String(describing: input.converted(to: UnitPower.femtowatts))
        default: output = String(describing: input.converted(to: UnitPower.watts))
            
        }
            
        return output
    }
    
        
    var body: some View {
        NavigationView{
            Form{
                Section(header: Text("Enter your Input value")){
                        TextField("Have a goal?", text: $inputValue)
                }
                
                Section(header: Text("Input")){
                    Picker("Input values", selection: $inputUnitValue){             			   ForEach(0..<inputUnits.count){ item in
                            Text(inputUnits[item])
                        }
                    }
                }
                
                Section(header: Text("Output")){
                    Picker("Output values", selection: $outputUnitValue){
                        ForEach(0..<outputUnits.count){ item in
                            Text(outputUnits[item])
                        }
                    }
                }
                
                Section(header: Text("Check your Output value")){
                    Text("\(after)")
                }
                
            }
            .navigationBarTitle("Pressure")
        }
    }
    
}

Thank you for your time

(Is there a way to use NumberFormatter with the computed String)

Answered by OOPer in 654784022

(Is there a way to use NumberFormatter with the computed String)

When you create a String for showing Measurement to users, you should better use MeasurementFormatter when converting to String.
Something like this:

Code Block struct PowerView: View {
    let outputFormatter: MeasurementFormatter = {
        let nf = NumberFormatter()
        //Set number style as you like...
        nf.numberStyle = .none
        nf.maximumSignificantDigits = 15
        nf.usesSignificantDigits = true
        let mf = MeasurementFormatter()
        mf.numberFormatter = nf
        mf.unitOptions = .providedUnit
        return mf
    }()
    
    //...
    var after: String {
        let input: Measurement<UnitPower>
        let output: String
        
        switch inputUnits[inputUnitValue] {
        case "watts": input = Measurement(value: Double(inputValue) ?? 0, unit: .watts)
        case "femtowatts": input = Measurement(value: Double(inputValue) ?? 0, unit: .femtowatts)
        default: input = Measurement(value: Double(inputValue) ?? 0, unit: .watts)
        }
        switch outputUnits[outputUnitValue] {
        case "watts": output =  outputFormatter.string(from: input.converted(to: .watts))
        case "femtowatts": output = outputFormatter.string(from: input.converted(to: .femtowatts))
        default: output = outputFormatter.string(from:  input.converted(to: .watts))
            
        }
        
        return output
    }
    //...
}

Boost

Answer 1

OOPer OP

Dec ’20

Accepted Answer

(Is there a way to use NumberFormatter with the computed String)

When you create a String for showing Measurement to users, you should better use MeasurementFormatter when converting to String.
Something like this:

Code Block struct PowerView: View {
    let outputFormatter: MeasurementFormatter = {
        let nf = NumberFormatter()
        //Set number style as you like...
        nf.numberStyle = .none
        nf.maximumSignificantDigits = 15
        nf.usesSignificantDigits = true
        let mf = MeasurementFormatter()
        mf.numberFormatter = nf
        mf.unitOptions = .providedUnit
        return mf
    }()
    
    //...
    var after: String {
        let input: Measurement<UnitPower>
        let output: String
        
        switch inputUnits[inputUnitValue] {
        case "watts": input = Measurement(value: Double(inputValue) ?? 0, unit: .watts)
        case "femtowatts": input = Measurement(value: Double(inputValue) ?? 0, unit: .femtowatts)
        default: input = Measurement(value: Double(inputValue) ?? 0, unit: .watts)
        }
        switch outputUnits[outputUnitValue] {
        case "watts": output =  outputFormatter.string(from: input.converted(to: .watts))
        case "femtowatts": output = outputFormatter.string(from: input.converted(to: .femtowatts))
        default: output = outputFormatter.string(from:  input.converted(to: .watts))
            
        }
        
        return output
    }
    //...
}

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