MediatorLiveData vs LiveData
I am not able to get the idea of MediatorLiveData while working with LiveData. In documentation it is mentioned that MediatorLiveData is a subclass of LiveData that will observe LiveData and react on onChanged method. My question is what's it's difference from having a function in observe of LiveData and do something with data if the new data is different?
For example, let's say I have query from Room Database that returns LiveData as below
@Query(“SELECT * FROM Users WHERE userid = :id”)
fun getUserById(id: String): LiveData<User>
If I want to use MediatorLiveData, I can have an extension as below
fun <T> LiveData<T>.distinctUntilChanged(): LiveData<T>
var lastValue: Any? = Any()
return MediatorLiveData<T>().apply
addSource(this@distinctUntilChanged)
if (it != lastValue)
lastValue = it
postValue(it)
And then use it in my Activity as
userDao.getUserById("someId").distinctUntilChanged()
.observe(this, user -> /*Do something with user*/)
Contrary to above scenario, I can just have a wrapper function inside observe method as below
var lastUser = null
userDao.getUserById("someId")
.observe(this, user ->
if (lastUser != user)
lastUser = user
/*Do something with user*/
)
Can anyone elaborate why I should use MediatorLiveData instead of just having simple check?
kotlin android-room android-livedata kotlin-extension
asked Nov 15 '18 at 1:58
musooffmusooff
603214
add a comment |
I am not able to get the idea of MediatorLiveData while working with LiveData. In documentation it is mentioned that MediatorLiveData is a subclass of LiveData that will observe LiveData and react on onChanged method. My question is what's it's difference from having a function in observe of LiveData and do something with data if the new data is different?
For example, let's say I have query from Room Database that returns LiveData as below
@Query(“SELECT * FROM Users WHERE userid = :id”)
fun getUserById(id: String): LiveData<User>
If I want to use MediatorLiveData, I can have an extension as below
fun <T> LiveData<T>.distinctUntilChanged(): LiveData<T>
var lastValue: Any? = Any()
return MediatorLiveData<T>().apply
addSource(this@distinctUntilChanged)
if (it != lastValue)
lastValue = it
postValue(it)
And then use it in my Activity as
userDao.getUserById("someId").distinctUntilChanged()
.observe(this, user -> /*Do something with user*/)
Contrary to above scenario, I can just have a wrapper function inside observe method as below
var lastUser = null
userDao.getUserById("someId")
.observe(this, user ->
if (lastUser != user)
lastUser = user
/*Do something with user*/
)
Can anyone elaborate why I should use MediatorLiveData instead of just having simple check?
kotlin android-room android-livedata kotlin-extension
asked Nov 15 '18 at 1:58
musooffmusooff
603214
proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08
add a comment |
I am not able to get the idea of MediatorLiveData while working with LiveData. In documentation it is mentioned that MediatorLiveData is a subclass of LiveData that will observe LiveData and react on onChanged method. My question is what's it's difference from having a function in observe of LiveData and do something with data if the new data is different?
For example, let's say I have query from Room Database that returns LiveData as below
@Query(“SELECT * FROM Users WHERE userid = :id”)
fun getUserById(id: String): LiveData<User>
If I want to use MediatorLiveData, I can have an extension as below
fun <T> LiveData<T>.distinctUntilChanged(): LiveData<T>
var lastValue: Any? = Any()
return MediatorLiveData<T>().apply
addSource(this@distinctUntilChanged)
if (it != lastValue)
lastValue = it
postValue(it)
And then use it in my Activity as
userDao.getUserById("someId").distinctUntilChanged()
.observe(this, user -> /*Do something with user*/)
Contrary to above scenario, I can just have a wrapper function inside observe method as below
var lastUser = null
userDao.getUserById("someId")
.observe(this, user ->
if (lastUser != user)
lastUser = user
/*Do something with user*/
)
Can anyone elaborate why I should use MediatorLiveData instead of just having simple check?
kotlin android-room android-livedata kotlin-extension
asked Nov 15 '18 at 1:58
musooffmusooff
603214
I am not able to get the idea of MediatorLiveData while working with LiveData. In documentation it is mentioned that MediatorLiveData is a subclass of LiveData that will observe LiveData and react on onChanged method. My question is what's it's difference from having a function in observe of LiveData and do something with data if the new data is different?
For example, let's say I have query from Room Database that returns LiveData as below
@Query(“SELECT * FROM Users WHERE userid = :id”)
fun getUserById(id: String): LiveData<User>
If I want to use MediatorLiveData, I can have an extension as below
fun <T> LiveData<T>.distinctUntilChanged(): LiveData<T>
var lastValue: Any? = Any()
return MediatorLiveData<T>().apply
addSource(this@distinctUntilChanged)
if (it != lastValue)
lastValue = it
postValue(it)
And then use it in my Activity as
userDao.getUserById("someId").distinctUntilChanged()
.observe(this, user -> /*Do something with user*/)
Contrary to above scenario, I can just have a wrapper function inside observe method as below
var lastUser = null
userDao.getUserById("someId")
.observe(this, user ->
if (lastUser != user)
lastUser = user
/*Do something with user*/
)
Can anyone elaborate why I should use MediatorLiveData instead of just having simple check?
kotlin android-room android-livedata kotlin-extension
kotlin android-room android-livedata kotlin-extension
asked Nov 15 '18 at 1:58
musooffmusooff
603214
asked Nov 15 '18 at 1:58
musooffmusooff
603214
asked Nov 15 '18 at 1:58
musooffmusooff
603214
asked Nov 15 '18 at 1:58
musooffmusooff
603214
asked Nov 15 '18 at 1:58
musooffmusooff
603214
603214
proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08
add a comment |
proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08
proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08
proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08
add a comment |
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proandroiddev.com/mediatorlivedata-to-the-rescue-5d27645b9bc3
– Roar Grønmo
Jan 10 at 22:08