Building the WeatherResponse Models

The WeatherResponse file contains Kotlin data classes that represent the JSON returned by OpenWeatherMap. These classes let Retrofit and Gson map JSON fields into Kotlin objects automatically.

data class WeatherResponse(
    val coord: Coord,
    val weather: List,
    val base: String,
    val main: Main,
    val visibility: Int,
    val wind: Wind,
    val clouds: Clouds,
    val dt: Long,
    val sys: Sys,
    val timezone: Int,
    val id: Int,
    val name: String,
    val cod: Int
)

data class Coord(
    val lon: Double,
    val lat: Double
)

data class Weather(
    val id: Int,
    val main: String,
    val description: String,
    val icon: String
)

data class Main(
    val temp: Double,
    val feels_like: Double,
    val temp_min: Double,
    val temp_max: Double,
    val pressure: Int,
    val humidity: Int,
    val sea_level: Int?,
    val grnd_level: Int?
)

data class Wind(
    val speed: Double,
    val deg: Int,
    val gust: Double?
)

data class Clouds(
    val all: Int
)

data class Sys(
    val type: Int?,
    val id: Int?,
    val country: String,
    val sunrise: Long,
    val sunset: Long
)

Code Explanation

Why Data Classes?

• A data class is great for storing structured data from APIs.
• Kotlin automatically gives useful features like toString(), equals(), and copy().
• These classes are easy to read and perfect for JSON mapping.

Top-Level Response Object

• WeatherResponse is the full response from the endpoint.
• It combines nested objects like main, wind, and sys.
• It also includes simple values such as city name (name) and status code (cod).

Nested Models

• Coord holds location coordinates (lon and lat).
• Weather holds weather condition details, and appears as a list because the API returns an array.
• Main holds temperature and pressure values.
• Wind, Clouds, and Sys each represent a specific part of the JSON.

Nullable Fields

• Some fields are optional in the API response, so they use nullable types like Int? or Double?.
• Examples include sea_level, grnd_level, and gust.
• Nullable types help prevent crashes when a field is missing.

Matching JSON Keys

• Field names in these classes match the JSON keys exactly, including names like feels_like.
• When names match, Gson can map data without extra annotations.
• If names did not match, you would use annotations like @SerializedName.

How the UI Uses This Model

• The repository returns a WeatherResponse object from the API call.
• The ViewModel stores it in state.
• The UI reads fields like weatherResponse.main.temp and weatherResponse.weather.firstOrNull()?.description.
• Strong typing makes these accesses safer than manual JSON parsing.