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# Hi, how to use the "Options" from the API to change the temperature from fahrenheit to celsius?

I have looked into the forecast io api document, and find there are options that can change the temperature to celsius. I'm not sure how to use the code they provided.

Thanks for your help!

## 2 Answers

PLUS

You could either use the options in the forecast.io call like you mention e.g.

```let forecastUrl = NSURL(string: "37.8267,-122.423?units=si", relativeToURL: baseUrl)
```

However be careful as that also changes lots of other units. The other way would be to create a new method in your Current.swift struct to change just the temperature to degrees using Maths similar to the dateStringFromUnixTime method for getting the current time.

Hi James This works like a charm! I will definitely try the other method as Matthew has clearly demonstrated below. Thanks a lot for your help, really appreciate it!

Thanks! I was going through the documentation but wasn't 100% sure how to use the "si". This worked like a charm!

For the simple route, you could just do a converstion method. I implemented the Swipe handler. Swipe left and it changes it to Celcius. Swipe right it switches it back.

```func celsiusFromFahrenheit(fahrenheit:Int) -> Int {
let c = ((Double(fahrenheit) - 32.0) * 5.0/9.0) // convert to Celsius
return String.localizedStringWithFormat("%.0f",c).toInt()! // properly round. (This is SO much easier in C#)

}
```

I added a View level property `isCelsiusSet` to hold the Value.

In the closure I use a ternary operator to set the temp:

```let temperature = inCelsius
? self.celsiusFromFahrenheit(currentWeather.temperature) //true
: currentWeather.temperature // false
```

(This could also be done in an if/else statement of course)

Obviously, you would need to use `temperature` when setting the label.

Finally I modified the `getCurrentWeatherData` signatuare to include a default parameter

```func getCurrentWeatherData(inCelsius:Bool = false) -> Void{
```

However, that was before I checked to see if the API supported Metric... so I'll probably go back and try that out. It was a good exercise, anyhow.

Thanks Matthew, this is really detail, will have a play around of your code!

Could you please tell me how to implement the swipe handler with the code you written. Thanks in advance.