Hi I just came across this where we are extending context wi

Question

Hi I just came across this where we are extending context with a toast function <https github com android android ktx pull 290> The call to toast becomes a lot nicer because we can just do `toast ` without worrying about `show ` etc My issue is whether this is actually a form of abuse on the extension function mechanism because Toast is not really an extension of context Similarly I have come across several examples where extension functions have been used to simply shave off a parameter from the original method call Any opinions

miszmaniac · Answer

IMAO this method should be called showToast just to make it clear what it actually does

Pascal How · Answer

Possibly but I am more concerned about whether extending Context is the right thing to do because extension functions were originally meant to augment enhance a class and in this example it looks like Context and Toast are not related

miszmaniac · Answer

I see your point here But this extension actually is helpful slightly smiling face

Pascal How · Answer

I totally agree The end result is lovely but it feels controversial

leosan · Answer

seems more like a problem of the `Context` itself being required for everything but since we have this god object makes sense these extensions for this context

miszmaniac · Answer

exactly It s how android works

gildor · Answer

I don t think that this is abuse and I don t think that this extension is controversial It s completely valid and convenient way to use extensions To bring some additions features to particular scope

gildor · Answer

In this case scope of context Context also has a lot of things for example resources and I don t see any particular reason why toast shouldn t be used as extension for context

Pascal How · Answer

Hmm ok

Pascal How · Answer

And how about this one ``` fun Context loadImageCenterCrop url String imageView ImageView Picasso withContext this load url centerCrop fit into imageView Elsewhere context loadImageCenterCrop <http example com image jpg> myImageView ```

miszmaniac · Answer

Why not do that on ImageView

leosan · Answer

this could be an extension of the imageView itself and would be better to get the context from the imageView

Pascal How · Answer

Yes exactly A better way is this ``` fun ImageView loadImageCenterCrop url String Picasso withContext this getContext load url centerCrop fit into this ```

Pascal How · Answer

Hence why I got a bit uneasy on things that extend Context

leosan · Answer

yes but with the `toast` would be weird making an extension of `String`

miszmaniac · Answer

We do that this way ```fun ImageView picassoLoad url String callback requestCreator RequestCreator gt Unit = null this context picasso load url apply callback invoke this into this ```

miszmaniac · Answer

and yes picasso is added to context D

julioyg · Answer

I get the context from the imageView if that makes sense

miszmaniac · Answer

me too picasso is added to context which is inside view

Pascal How · Answer

Yea definitely That s like in the second example I showed where I am extending ImageView instead slightly smiling face But saying that the first example is still an extension function but used in the wrong way

Pascal How · Answer

My point was that even though both ``` fun Context loadImageCenterCrop url String imageView ImageView Picasso withContext this load url centerCrop fit into imageView Elsewhere context loadImageCenterCrop <http example com image jpg> myImageView ``` and ``` fun ImageView loadImageCenterCrop url String Picasso withContext this getContext load url centerCrop fit into this ``` both make your code more concise and both use the extension function mechanism the first approach is bad because context has nothing to do with `loadImageCenterCrop`

miszmaniac · Answer

yea i just use ```val Context picasso Picasso get = Picasso with this ``` Context works as service locator anyway so no harm done here

gildor · Answer

Don t like this solution also you create an instance of Picasso for each call

miszmaniac · Answer

It does not We ve used Picasso setSingletonInstance in application and this method is just returning this instance

gildor · Answer

Okay I see

Makoto · Answer

Anko does this <https github com Kotlin anko wiki Anko Commons E2 80 93 Dialogs>

Makoto · Answer

``` toast Hi there toast R string message longToast Wow such duration ```

Pascal How · Answer

Thanks all for your input +1 So I guess the conclusion is that for `Toast` it is fine to extend `Context` because it is like bringing new additions to the scope and it is convenient but in the case of ``` fun Context loadImageCenterCrop url String imageView ImageView Picasso withContext this load url centerCrop fit into imageView ``` Even though essentially it is doing the same thing as extending `Context` with `Toast` it is not fine because it is better to extend `ImageView`

gildor · Answer

Yes also each view already contains context no need to pass context and ImageView separately Also it s just looks more natural to have such method on imageView