Scala存在两种参数传递的方式。 Pass-by-Value:按值传递 Pass-by-Name:按名传递 按值传递 默认情况下,Scala的参数是按照值传递的。 def and(x: Boolean, y: Boolean) = x && y 对于如下调用语句: and(false, s.contains("horance")) 表达式s.contains("horance")首先会被立即求值,然后才会传递给参数y;...
So the issue is how can you pass a by-name-parameter to a method that takes a function as a parameter without having to do: 1. scala> def takesFunc(func: () => Int) = println(func()) 2. takesFunc: (() => Int)Unit 3. scala> def send(x: => Int) = takesFunc(() => x...
Here’s aScalacall-by-nameexample. I’ll show the normal approach to writing a method and passing in a parameter, and then show a call-by-name (pass by name) example. 1) A “normal” Scala method (call-by-value) Here I show how to pass a parameter to a method “normally,” i....
Sample of a method declared to accept call by value parameter passing,def add(a:Int , b:Int){ var sum = a + b ; println("sum = " + sum); } The call will pass values that will be copied to variables a and b, and the operations on a and b will be independent of the actual...
Call by name is used in Scalawhen the program needs to pass an expression or a block of code as a parameter to a function. The code block passed as call by name in the program will not get executed until it is called by the function. ...
例如,假设在登录界面的代码中分别使用user_name和pass_word获取用户输入的用户名和密码,然后使用下面的代码拼接SQL语句,试图返回数据表中以user_name为用户名且以pass_word...如果在代码中不是直接拼接SQL语句,而是使用参数化查询,可以轻易防范这种攻击。...另外,对数据进行编码(例如,BASE64编码或MD5摘要)或净化(例...
Two optimizations to avoid re-computation: (1) keep a list of explored paths, pass that into the next Path calculation (2) pass the current endState to the constructor of the next Path so the next Path won't have to recompute the last Path's endState all over again using the history...
// the main() method, where we pass timeFlies into oncePerSecond. def main(args: Array[String]) { oncePerSecond(timeFlies) } } Because of the simplicity of that demo and the use of the word callback as a variable name, this example was very easy for me to digest. ...
Each time a by-name parameter is used inside a function, it gets evaluated into a value. If a value is passed to the function then there is no effect, but if a function is passed then that function is invoked for every usage. When you pass a function to a by-name parameter, make ...
You can exclude whole classes or packages by name. Pass a semicolon separated list of regexes to theexcludedPackagesoption. For example: -P:scoverage:excludedPackages:.*\.utils\..*;.*\.SomeClass;org\.apache\..* The regular expressions are matched against the fully qualified class name, and...