编写接受具有特定方法的对象的方法的语法
我想编写一个通用的辅助方法：
def using(closeable: [B has close() method], callback: [B has close() method] => A): A {
try {
callback(closeable)
} finally {
closeable.close()
}
}
目的是我可以将它与任何具有 close() 方法的东西一起使用：
using(new FileInputStream(...)) {
stream => stream.read()
}
using(dataSource.getConnection) {
conn => using(conn.createStatement()) {
statement => using(statement.executeQuery("...")) {
rs => rs.getString(1)
}
}
}
我正在寻找的是它的命名方式，这样我就可以自己搜索语法，以及语法本身。
I want to write a generic helper method:
def using(closeable: [B has close() method], callback: [B has close() method] => A): A {
try {
callback(closeable)
} finally {
closeable.close()
}
}
with the intent being that I can use this with anything that has a close() method:
using(new FileInputStream(...)) {
stream => stream.read()
}
using(dataSource.getConnection) {
conn => using(conn.createStatement()) {
statement => using(statement.executeQuery("...")) {
rs => rs.getString(1)
}
}
}
What I'm looking for is how this is named, such that I could have searched for the syntax myself, and the syntax itself.
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评论（3）
完整地给出它
（您也可以编写
A {def close()}而不是A with Closeable）测试：
输出：
To give it in full
(you may also write
A {def close()}rather thanA with Closeable)A test:
output:
这称为结构类型。
This is called a structural type.
Debilski 是对的，其语法是
close: { def close() }编辑：这里有一个替代链接 .NET 的 Scala 实现，类似于您想要基于对象及其 apply 方法使用的 using 构造。
Debilski is right, the syntax for that would be
closable: { def close() }Edit: Here's a link to an alternative Scala implementation of the .NET like using construct you want to use based on an object and it's apply method.