在Kotlin中将String转换为T

让创建Preference的人告诉您如何将T转换为String或从String转换为T.添加(T) -> String和(String) -> T作为构造函数参数.

class Preference<T>(
    private val key: String,
    private val defaultValue: T,
    private val convertToString: (T) -> String,
    private val convertFromString: (String) -> T
) : ReadWriteProperty<AppPreferences, T> {

    override fun getValue(thisRef: AppPreferences, property: KProperty<*>): T {
        return convertFromString(properties.getProperty(key)) ?: defaultValue
    }

    override fun setValue(thisRef: AppPreferences, property: KProperty<*>, value: T) {
        properties.setProperty(key, convertToString(value))
        saveProperties()
    }
}

然后，您可以为特定类型的首选项创建函数--String、Int、Boolean等.这些方法将创建Preference的实例，并传入(T) -> String和(String) -> T参数，然后返回该实例.

fun preference(key: String, defaultValue: String) = Preference(
    key, defaultValue, { it }, { it }
)

fun preference(key: String, defaultValue: Int) = Preference(
    key, defaultValue, Int::toString, String::toInt
)

fun preference(key: String, defaultValue: Boolean) = Preference(
    key, defaultValue, Boolean::toString, String::toBoolean
)