scala.util

# Try

#### sealed abstract class Try[+T] extends AnyRef

The `Try` type represents a computation that may either result in an exception, or return a successfully computed value. It's similar to, but semantically different from the scala.util.Either type.

Instances of `Try[T]`, are either an instance of scala.util.Success[T] or scala.util.Failure[T].

For example, `Try` can be used to perform division on a user-defined input, without the need to do explicit exception-handling in all of the places that an exception might occur.

Example:

    import scala.util.{Try, Success, Failure}

    def divide: Try[Int] = {
      val dividend = Try(Console.readLine("Enter an Int that you'd like to divide:\n").toInt)
      val divisor = Try(Console.readLine("Enter an Int that you'd like to divide by:\n").toInt)
      val problem = dividend.flatMap(x => divisor.map(y => x/y))
      problem match {
        case Success(v) =>
          println("Result of " + dividend.get + "/"+ divisor.get +" is: " + v)
          Success(v)
        case Failure(e) =>
          println("You must've divided by zero or entered something that's not an Int. Try again!")
          println("Info from the exception: " + e.getMessage)
          divide
      }
    }

An important property of `Try` shown in the above example is its ability to pipeline, or chain, operations, catching exceptions along the way. The `flatMap` and `map` combinators in the above example each essentially pass off either their successfully completed value, wrapped in the `Success` type for it to be further operated upon by the next combinator in the chain, or the exception wrapped in the `Failure` type usually to be simply passed on down the chain. Combinators such as `rescue` and `recover` are designed to provide some type of default behavior in the case of failure.

Note: only non-fatal exceptions are caught by the combinators on `Try` (see scala.util.control.NonFatal). Serious system errors, on the other hand, will be thrown.

Note:: all Try combinators will catch exceptions and return failure unless otherwise specified in the documentation.

`Try` comes to the Scala standard library after years of use as an integral part of Twitter's stack.

Since

  2.10

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2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Instance Constructors

1. #### new Try()

### Type Members

1. #### class WithFilter extends AnyRef

   We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

### Abstract Value Members

1. #### abstract def failed: Try[Throwable]

   Completes this `Try` with an exception wrapped in a `Success`.

   Completes this `Try` with an exception wrapped in a `Success`. The exception is either the exception that the `Try` failed with (if a `Failure`) or an `UnsupportedOperationException`.

2. #### abstract def filter(p: (T) ⇒ Boolean): Try[T]

   Converts this to a `Failure` if the predicate is not satisfied.

3. #### abstract def flatMap[U](f: (T) ⇒ Try[U]): Try[U]

   Returns the given function applied to the value from this `Success` or returns this if this is a `Failure`.

4. #### abstract def flatten[U](implicit ev: <:<[T, Try[U]]): Try[U]

   Transforms a nested `Try`, ie, a `Try` of type `Try[Try[T]]`, into an un-nested `Try`, ie, a `Try` of type `Try[T]`.

5. #### abstract def foreach[U](f: (T) ⇒ U): Unit

   Applies the given function `f` if this is a `Success`, otherwise returns `Unit` if this is a `Failure`.

   Applies the given function `f` if this is a `Success`, otherwise returns `Unit` if this is a `Failure`.

   Note: If `f` throws, then this method may throw an exception.

6. #### abstract def get: T

   Returns the value from this `Success` or throws the exception if this is a `Failure`.

7. #### abstract def isFailure: Boolean

   Returns `true` if the `Try` is a `Failure`, `false` otherwise.

8. #### abstract def isSuccess: Boolean

   Returns `true` if the `Try` is a `Success`, `false` otherwise.

9. #### abstract def map[U](f: (T) ⇒ U): Try[U]

   Maps the given function to the value from this `Success` or returns this if this is a `Failure`.

10. #### abstract def recover[U >: T](f: PartialFunction[Throwable, U]): Try[U]

    Applies the given function `f` if this is a `Failure`, otherwise returns this if this is a `Success`.

    Applies the given function `f` if this is a `Failure`, otherwise returns this if this is a `Success`. This is like map for the exception.

11. #### abstract def recoverWith[U >: T](f: PartialFunction[Throwable, Try[U]]): Try[U]

    Applies the given function `f` if this is a `Failure`, otherwise returns this if this is a `Success`.

    Applies the given function `f` if this is a `Failure`, otherwise returns this if this is a `Success`. This is like `flatMap` for the exception.

### Concrete Value Members

1. #### final def !=(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from Try[T] to any2stringadd[Try[T]] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (Try[T], B)

   Implicit information
     This member is added by an implicit conversion from Try[T] to ArrowAssoc[Try[T]] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

5. #### final def ==(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

6. #### final def asInstanceOf[T0]: T0

   Definition Classes
     Any

7. #### def clone(): AnyRef

   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )

8. #### def ensuring(cond: (Try[T]) ⇒ Boolean, msg: ⇒ Any): Try[T]

   Implicit information
     This member is added by an implicit conversion from Try[T] to Ensuring[Try[T]] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Try[T]) ⇒ Boolean): Try[T]

   Implicit information
     This member is added by an implicit conversion from Try[T] to Ensuring[Try[T]] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: Boolean, msg: ⇒ Any): Try[T]

    Implicit information
      This member is added by an implicit conversion from Try[T] to Ensuring[Try[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): Try[T]

    Implicit information
      This member is added by an implicit conversion from Try[T] to Ensuring[Try[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

13. #### def equals(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### def finalize(): Unit

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )

15. #### def formatted(fmtstr: String): String

    Returns string formatted according to given `format` string.

    Returns string formatted according to given `format` string. Format strings are as for `String.format` (@see java.lang.String.format).

    Implicit information
      This member is added by an implicit conversion from Try[T] to StringFormat[Try[T]] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

17. #### def getOrElse[U >: T](default: ⇒ U): U

    Returns the value from this `Success` or the given `default` argument if this is a `Failure`.

    Returns the value from this `Success` or the given `default` argument if this is a `Failure`.

    Note:: This will throw an exception if it is not a success and default throws an exception.

18. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

19. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

20. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

21. #### final def notify(): Unit

    Definition Classes
      AnyRef

22. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

23. #### def orElse[U >: T](default: ⇒ Try[U]): Try[U]

    Returns this `Try` if it's a `Success` or the given `default` argument if this is a `Failure`.

24. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

25. #### def toOption: Option[T]

    Returns `None` if this is a `Failure` or a `Some` containing the value if this is a `Success`.

26. #### def toString(): String

    Definition Classes
      AnyRef → Any

27. #### def transform[U](s: (T) ⇒ Try[U], f: (Throwable) ⇒ Try[U]): Try[U]

    Completes this `Try` by applying the function `f` to this if this is of type `Failure`, or conversely, by applying `s` if this is a `Success`.

28. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

29. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

30. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

31. #### final def withFilter(p: (T) ⇒ Boolean): WithFilter

    Creates a non-strict filter, which eventually converts this to a `Failure` if the predicate is not satisfied.

    Creates a non-strict filter, which eventually converts this to a `Failure` if the predicate is not satisfied.

    Note: unlike filter, withFilter does not create a new Try. Instead, it restricts the domain of subsequent `map`, `flatMap`, `foreach`, and `withFilter` operations.

    As Try is a one-element collection, this may be a bit overkill, but it's consistent with withFilter on Option and the other collections.

    p

      the predicate used to test elements.

    returns

      an object of class `WithFilter`, which supports `map`, `flatMap`, `foreach`, and `withFilter` operations. All these operations apply to those elements of this Try which satisfy the predicate `p`.

    Annotations
      @inline()

32. #### def →[B](y: B): (Try[T], B)

    Implicit information
      This member is added by an implicit conversion from Try[T] to ArrowAssoc[Try[T]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Try[T] to any2stringadd[Try[T]]

### Inherited by implicit conversion StringFormat from Try[T] to StringFormat[Try[T]]

### Inherited by implicit conversion Ensuring from Try[T] to Ensuring[Try[T]]

### Inherited by implicit conversion ArrowAssoc from Try[T] to ArrowAssoc[Try[T]]

### Ungrouped