You can use ML Kit to translate text between languages. ML Kit currently supports translation between 59 languages .
Before you begin
- If you have not already added Firebase to your app, do so by following the steps in the getting started guide .
- Include the ML Kit libraries in your Podfile:
pod 'Firebase/MLNLTranslate', '6.25.0'
.xcworkspace. - In your app, import Firebase:
Swift
import Firebase
Objective-C
@import Firebase ;
Translate a string of text
To translate a string between two languages:
-
Create a
Translatorobject, configuring it with the source and target languages:Swift
// Create an English-German translator: let options = TranslatorOptions ( sourceLanguage : . en , targetLanguage : . de ) let englishGermanTranslator = NaturalLanguage . naturalLanguage (). translator ( options : options )Objective-C
// Create an English-German translator: FIRTranslatorOptions * options = [[ FIRTranslatorOptions alloc ] initWithSourceLanguage : FIRTranslateLanguageEN targetLanguage : FIRTranslateLanguageDE ]; FIRTranslator * englishGermanTranslator = [[ FIRNaturalLanguage naturalLanguage ] translatorWithOptions : options ];If you don't know the language of the input text, you can use the language identification API first. (But be sure you don't keep too many language models on the device at once.)
-
Make sure the required translation model has been downloaded to the device. Don't call
translate(_:completion:)until you know the model is available.Swift
let conditions = ModelDownloadConditions ( allowsCellularAccess : false , allowsBackgroundDownloading : true ) englishGermanTranslator . downloadModelIfNeeded ( with : conditions ) { error in guard error == nil else { return } // Model downloaded successfully. Okay to start translating. }Objective-C
FIRModelDownloadConditions * conditions = [[ FIRModelDownloadConditions alloc ] initWithAllowsCellularAccess : NO allowsBackgroundDownloading : YES ]; [ englishGermanTranslator downloadModelIfNeededWithConditions : conditions completion : ^ ( NSError * _Nullable error ) { if ( error != nil ) { return ; } // Model downloaded successfully. Okay to start translating. }];Language models are around 30MB, so don't download them unnecessarily, and only download them using WiFi, unless the user has specified otherwise. You should also delete unneeded models. See Explicitly manage translation models .
-
After you confirm the model has been downloaded, pass a string of text in the source language to
translate(_:completion:):Swift
englishGermanTranslator . translate ( text ) { translatedText , error in guard error == nil , let translatedText = translatedText else { return } // Translation succeeded. }Objective-C
[ englishGermanTranslator translateText : text completion : ^ ( NSString * _Nullable translatedText , NSError * _Nullable error ) { if ( error != nil || translatedText == nil ) { return ; } // Translation succeeded. }];ML Kit translates the text to the target language you configured and passes the translated text to the completion handler.
Explicitly manage translation models
When you use the translation API as described above, ML Kit automatically downloads language-specific translation models to the device as required. You can also explicitly manage the translation models you want available on the device by using ML Kit's translation model management API. This can be useful if you want to download models ahead of time, or delete unneeded models from the device.
To get the translation models stored on the device:
Swift
let
localModels
=
ModelManager
.
modelManager
().
downloadedTranslateModels
Objective-C
NSSet<FIRTranslateRemoteModel
*
>
*
localModels
=
[
FIRModelManager
modelManager
].
downloadedTranslateModels
;
To delete a model:
Swift
// Delete the German model if it's on the device.
let
deModel
=
TranslateRemoteModel
.
translateRemoteModel
(
language
:
.
de
)
ModelManager
.
modelManager
().
deleteDownloadedModel
(
deModel
)
{
error
in
guard
error
==
nil
else
{
return
}
// Model deleted.
}
Objective-C
// Delete the German model if it's on the device.
FIRTranslateRemoteModel
*
deModel
=
[
FIRTranslateRemoteModel
translateRemoteModelWithLanguage
:
FIRTranslateLanguageDE
];
[[
FIRModelManager
modelManager
]
deleteDownloadedModel
:
deModel
completion
:
^
(
NSError
*
_Nullable
error
)
{
if
(
error
!=
nil
)
{
return
;
}
// Model deleted.
}];
To download a model:
Swift
// Download the French model.
let
frModel
=
TranslateRemoteModel
.
translateRemoteModel
(
language
:
.
fr
)
// Keep a reference to the download progress so you can check that the model
// is available before you use it.
progress
=
ModelManager
.
modelManager
().
download
(
frModel
,
conditions
:
ModelDownloadConditions
(
allowsCellularAccess
:
false
,
allowsBackgroundDownloading
:
true
)
)
If you want to get the download status with NotificationCenter
, register
observers for firebaseMLModelDownloadDidSucceed
and firebaseMLModelDownloadDidFail
. Be sure to use a weak reference to self
in the observer block, since downloads can take some time, and the originating
object can be freed by the time the download finishes. For example:
NotificationCenter
.
default
.
addObserver
(
forName
:
.
firebaseMLModelDownloadDidSucceed
,
object
:
nil
,
queue
:
nil
)
{
[
weak
self
]
notification
in
guard
let
strongSelf
=
self
,
let
userInfo
=
notification
.
userInfo
,
let
model
=
userInfo
[
ModelDownloadUserInfoKey
.
remoteModel
.
rawValue
]
as
?
TranslateRemoteModel
,
model
==
frModel
else
{
return
}
// The model was downloaded and is available on the device
}
NotificationCenter
.
default
.
addObserver
(
forName
:
.
firebaseMLModelDownloadDidFail
,
object
:
nil
,
queue
:
nil
)
{
[
weak
self
]
notification
in
guard
let
strongSelf
=
self
,
let
userInfo
=
notification
.
userInfo
,
let
model
=
userInfo
[
ModelDownloadUserInfoKey
.
remoteModel
.
rawValue
]
as
?
TranslateRemoteModel
else
{
return
}
let
error
=
userInfo
[
ModelDownloadUserInfoKey
.
error
.
rawValue
]
// ...
}
Objective-C
// Download the French model.
FIRModelDownloadConditions
*
conditions
=
[[
FIRModelDownloadConditions
alloc
]
initWithAllowsCellularAccess
:
NO
allowsBackgroundDownloading
:
YES
];
FIRTranslateRemoteModel
*
frModel
=
[
FIRTranslateRemoteModel
translateRemoteModelWithLanguage
:
FIRTranslateLanguageFR
];
// Keep a reference to the download progress so you can check that the model
// is available before you use it.
self
.
downloadProgress
=
[[
FIRModelManager
modelManager
]
downloadModel
:
frModel
conditions
:
conditions
];
If you want to get the download status with NSNotificationCenter
, register
observers for FIRModelDownloadDidSucceedNotification
and FIRModelDownloadDidFailNotification
. Be sure to use a weak reference to self
in the observer block, since downloads can take some time, and the
originating object can be freed by the time the download finishes.
__block
MyViewController
*
weakSelf
=
self
;
[
NSNotificationCenter
.
defaultCenter
addObserverForName
:
FIRModelDownloadDidSucceedNotification
object
:
nil
queue
:
nil
usingBlock
:
^
(
NSNotification
*
_Nonnull
note
)
{
if
(
weakSelf
==
nil
|
note
.
userInfo
==
nil
)
{
return
;
}
FIRTranslateRemoteModel
*
model
=
note
.
userInfo
[
FIRModelDownloadUserInfoKeyRemoteModel
];
if
([
model
isKindOfClass
:
[
FIRTranslateRemoteModel
class
]]
&&
model
==
frModel
)
{
// The model was downloaded and is available on the device
}
}];
[
NSNotificationCenter
.
defaultCenter
addObserverForName
:
FIRModelDownloadDidFailNotification
object
:
nil
queue
:
nil
usingBlock
:
^
(
NSNotification
*
_Nonnull
note
)
{
if
(
weakSelf
==
nil
|
note
.
userInfo
==
nil
)
{
return
;
}
NSError
*
error
=
note
.
userInfo
[
FIRModelDownloadUserInfoKeyError
];
}];
