org.scalatest.enablers.Readability.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 readable matcher syntax.
 *
 * 
 * A Readability[T] provides access to the "readable nature" of type T in such
 * a way that be readable matcher syntax can be used with type T. A T
 * can be any type for which the concept of being readable makes sense, such as java.io.File.
 * You can enable the be readable matcher syntax on your own type U by defining a
 * Readability[U] for the type and making it available implicitly.
 * 
 * 

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

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

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

import scala.reflect.Selectable.reflectiveSelectable

  /**
   * Enable Readability implementation for java.io.File.
   *
   * @tparam FILE any subtype of java.io.File
   * @return Readability[FILE] that supports java.io.File in be readable syntax
   */
  implicit def readabilityOfFile[FILE <: java.io.File]: Readability[FILE] =
    new Readability[FILE] {
      def isReadable(file: FILE): Boolean = file.canRead
    }

  import scala.language.reflectiveCalls

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

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