# SingleEvent.kt

    /*
     * The MIT License
     *
     * Original work sponsored and donated by The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     * Copyright (C) 2021 The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy of
     * this software and associated documentation files (the "Software"), to deal in
     * the Software without restriction, including without limitation the rights to
     * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
     * of the Software, and to permit persons to whom the Software is furnished to do
     * so, subject to the following conditions:
     *
     *
     * The above copyright notice and this permission notice shall be included in all
     * copies or substantial portions of the Software.
     *
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     * SOFTWARE.
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    package dk.nsp.mingraviditet.util.livedata

    import dk.nsp.mingraviditet.util.commonsense_helpers.SetOnceBool
    import dk.nsp.mingraviditet.util.commonsense_helpers.getValue
    import dk.nsp.mingraviditet.util.commonsense_helpers.setValue

    // As per https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150
    /**
     * Used as a wrapper for data that is exposed via a LiveData that represents an event.
     */
    class SingleEvent<out T>(private val value: T) {
        private var hasBeenHandled: Boolean by SetOnceBool(false)

        /**
         * Returns the wrapped value if it hasn't been handled else returns null
         * @return T? [SingleEvent.value]
         */
        fun getIfNotHandled(): T? {

            return if (hasBeenHandled) {
                null
            } else {
                hasBeenHandled = true
                value
            }
        }

        /**
         * Convenience to peek the value even if it has been handled
         * @return [value]
         */
        fun peekValue() = value
    }