Kotlin的可空性和LiveData [英] Nullability and LiveData with Kotlin

问题描述

我想将LiveData与Kotlin一起使用，并且其值不能为null.您如何处理?也许是LiveData的包装?在这里搜索良好的模式.. 例如:

I want to use LiveData with Kotlin and have values that should not be null. How do you deal with this? Perhaps a wrapper around LiveData? Searching for good patterns here .. As an example:

class NetworkDefinitionProvider : MutableLiveData<NetworkDefinition>() {
    val allDefinitions = mutableListOf(RinkebyNetworkDefinition(), MainnetNetworkDefinition(), RopstenNetworkDefinition())

    init {
        value = allDefinitions.first()
    }

    fun setCurrent(value: NetworkDefinition) {
        setValue(value)
    }
}

我知道访问时值不会为空-但我将始终必须检查是否为空或这些丑陋的!!周围.

I know value will not be null when accessing - but I will always have to check for null or have these ugly !!'s around.

推荐答案

我创建了扩展属性.它不是很漂亮，但是 很简单.

I created an extension property. It's not super pretty, but it is pretty straightforward.

val <T> LiveData<T>.valueNN
    get() = this.value!!

用法

spinner.loading = myLiveData.valueNN.homeState.loading

我不愿意将"NN"作为良好的命名约定，但这超出了问题的范围:)

I'm not sold on appending "NN" as a good naming convention, but that's beyond the scope of the question :)

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