org.scalatest.enablers.Writability.scala Maven / Gradle / Ivy

/*
 * Copyright 2001-2013 Artima, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.scalatest.enablers

import Aggregating.tryEquality
import org.scalactic.Equality
import org.scalatest.FailureMessages
import scala.annotation.tailrec
import scala.collection.GenTraversable

/**
 * Supertrait for typeclasses that enable the be writable matcher syntax.
 *
 * 
 * A Writability[T] provides access to the "writable nature" of type T in such
 * a way that be writable matcher syntax can be used with type T. A T
 * can be any type for which the concept of being writable makes sense, such as java.io.File. ScalaTest provides
 * implicit implementation for java.io.File. You can enable the be writable matcher syntax on your own
 * type U by defining a Writability[U] for the type and making it available implicitly.
 * 
 * 

 * ScalaTest provides an implicit Writability instance for java.io.File and arbitary
 * object with isWritable() or isWritable in the Writability companion object.
 * 
 */
trait Writability[-T] {

  /**
   * Determines whether the passed thing is writable, i.e., the passed file is writable.
   *
   * @param thing the thing to check for writability
   * @return true if the passed thing is writable, false otherwise
   */
  def isWritable(thing: T): Boolean
}

/**
 * Companion object for Writability that provides implicit implementations for the following types:
 *
 * 
 * java.io.File
 * arbitary object with a isWritable() method that returns Boolean
 * arbitary object with a parameterless isWritable method that returns Boolean
 * 
 */
object Writability {

import scala.reflect.Selectable.reflectiveSelectable

  /**
   * Enable Writability implementation for java.io.File.
   *
   * @tparam FILE any subtype of java.io.File
   * @return Writability[FILE] that supports java.io.File in be writable syntax
   */
  implicit def writabilityOfFile[FILE <: java.io.File]: Writability[FILE] =
    new Writability[FILE] {
      def isWritable(file: FILE): Boolean = file.canWrite
    }

  import scala.language.reflectiveCalls

  /**
   * Enable Writability implementation for any arbitrary object with a isWritable() method that returns Boolean
   *
   * @tparam T any type that has a isWritable() method that returns Boolean
   * @return Writability[T] that supports T in be writable syntax
   */
  implicit def writabilityOfAnyRefWithIsWritableMethod[T <: AnyRef { def isWritable(): Boolean}]: Writability[T] = 
    new Writability[T] {
      def isWritable(obj: T): Boolean = obj.isWritable()
    }

  /**
   * Enable Writability implementation for any arbitrary object with a parameterless isWritable method that returns Boolean
   *
   * @tparam T any type that has a parameterless isWritable method that returns Boolean
   * @return Writability[T] that supports T in be writable syntax
   */
  implicit def writabilityOfAnyRefWithParameterlessIsWritableMethod[T <: AnyRef { def isWritable: Boolean}]: Writability[T] = 
    new Writability[T] {
      def isWritable(obj: T): Boolean = obj.isWritable
    }
}