我似乎有一个相对简单的问题:我确实有一些代码从http下载文件并执行解压缩操作。这两个代码看起来非常相似:
def downloadFile(url: URL, filename: String) {
var out: OutputStream = null
var in: InputStream = null
try {
val outPutFile = new File(filename)
if (outPutFile.exists())
{
outPutFile.delete()
}
val uc = url.openConnection()
val connection = uc.asInstanceOf[HttpURLConnection]
connection.setRequestMethod("GET")
in = connection.getInputStream()
out = new BufferedOutputStream(new FileOutputStream(filename))
copy(in, out)
} catch {
case e: Exception => println(e.printStackTrace())
}
out.close()
in.close()
}
def unzipFile(file: File): String = {
var out: OutputStream = null
val outputFileName = "uncompressed" + file.getName()
println("trying to acess " + file.getName() + file.getAbsoluteFile())
val in = new BZip2CompressorInputStream(new FileInputStream(file))
val outfile = new File(outputFileName)
if (outfile.exists()) {
outfile.delete()
}
out = new FileOutputStream(outputFileName)
copy(in, out)
in.close()
out.close()
return outputFileName
}
def copy(in: InputStream, out: OutputStream) {
val buffer: Array[Byte] = new Array[Byte](1024)
var sum: Int = 0
Iterator.continually(in.read(buffer)).takeWhile(_ != -1).foreach({ n => out.write(buffer, 0, n); (sum += buffer.length); println(sum + " written to output "); })
}
是否有一种方法可以将下载/解压缩方法重写为一个方法,并将构造函数提取出来,以实现类似依赖注入的行为?
我认为你要问的问题是你有功能的情况下,有相同的需求开始和/或结束,但中间部分可以在每次调用的基础上有所不同。如果这就是你想要的,那么通过传递中间部分来解决这个问题,就像这样:
def doSomething(func: => Unit){
//Do common stuff here
//Invoke passed in behavior
func
//Do common end stuff here
}
那么你可以像这样在另一个函数中使用它:
def downloadFile(url: URL, filename: String) {
doSomething{
//You have access to url and filename here due to closure
}
}
这样,如果这两个函数(downloadFile
和unzipFile
)之间有共同的关注点/功能,您可以在doSomething
中捕获它,然后只允许调用函数指定特定于该函数的行为。
此模式类似于贷款模式,也可能与OO世界中的模板方法有关