Which one recommended to use postValue() in IO thread or setValue() on main thread android kotlin li-CodePudding

I have view model and I use live data. Which one is recommended to use and why? In main thread setValue or in IO thread postValue() or in main thread postValue()

fun getProductInfoFromWebService(barcode: String, url: String) {
    viewModelScope.launch(Dispatchers.IO) {
        val response = productInfoRepo.getProductInfoFromWebService(barcode, url)
        withContext(Dispatchers.Main) {
            _productInfoFromWebService.value = response
        }
    }
}


fun getProductInfoFromWebService(barcode: String, url: String) {
    viewModelScope.launch(Dispatchers.IO) {
        val response = productInfoRepo.getProductInfoFromWebService(barcode, url)
        withContext(Dispatchers.Main) {
            _productInfoFromWebService.postValue(response)
        }
    }
}


    fun getProductInfoFromWebService(barcode: String, url: String) {
    viewModelScope.launch(Dispatchers.IO) {
        val response = productInfoRepo.getProductInfoFromWebService(barcode, url)
        _productInfoFromWebService.postValue(response)
    }
}

CodePudding user response：

The first snippet uses withContext(Dispatchers.Main) to switch to the main thread before updating the value of _productInfoFromWebService. This is necessary because LiveData objects can only be modified on the main thread.

The second and third snippets use postValue() to update the value of _productInfoFromWebService. This is a method of the MutableLiveData class that allows you to update the value of the LiveData object from any thread. It automatically switches to the main thread before updating the value, so you don't need to use withContext(Dispatchers.Main) as in the first snippet.

In terms of which one is "best," it really depends on your personal preference and the needs of your application. All three snippets will work correctly, so you can choose the one that you think is the most readable and maintainable for your codebase.

postValue() and setValue() are both methods of the MutableLiveData class that allow you to update the value of a LiveData object. The main difference between the two is how they handle updates on different threads.

setValue() can only be called on the main thread, so it is useful if you want to update the value of a LiveData object from the main thread. However, if you try to call setValue() from a background thread, it will throw an exception.

On the other hand, postValue() can be called from any thread, and it will automatically switch to the main thread before updating the value of the LiveData object. This makes it more flexible than setValue(), as you can use it to update the value of a LiveData object from a background thread without having to worry about thread-safety issues.

So to answer your question, postValue() is not always best, but it is generally more flexible and easier to use than setValue() when you need to update the value of a LiveData object from a background thread. However, you should use setValue() if you need to update the value of a LiveData object from the main thread and you want to avoid the overhead of switching threads.