code for 0x14 context managers

mike-kfed · mike-kfed · commit 04642349eda2 · 2021-07-02T17:40:40.000+02:00
diff --git a/14_context_manager/python/context_manager.py b/14_context_manager/python/context_manager.py
@@ -0,0 +1,19 @@
+class FileManager():
+    def __init__(self, filename, mode):
+        self.filename = filename
+        self.mode = mode
+        self.file = None
+
+    def __enter__(self):
+        self.file = open(self.filename, self.mode)
+        return self.file
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        self.file.close()
+
+
+if __name__ == "__main__":
+    with FileManager('test.txt', 'w') as f:
+        f.write('Test')
+
+    print(f.closed)
diff --git a/14_context_manager/rust/context_manager.rs b/14_context_manager/rust/context_manager.rs
@@ -0,0 +1,44 @@
+use std::fs::File;
+use std::io::{self, Write};
+
+struct FileManager {
+    filename: std::path::PathBuf,
+    mode: char,
+    file: Option<File>,
+}
+
+impl FileManager {
+    fn new(filename: impl AsRef<std::path::Path>, mode: char) -> FileManager {
+        FileManager {
+            filename: filename.as_ref().to_owned(),
+            mode,
+            file: None,
+        }
+    }
+
+    fn with<F>(self: &mut Self, f: F) -> io::Result<()>
+    where
+        F: Fn(&mut File) -> io::Result<()>,
+    {
+        if self.mode == 'w' {
+            self.file = Some(File::create(&self.filename)?);
+            f(&mut self.file.as_mut().unwrap())?;
+            self.file = None;
+        }
+        Ok(())
+    }
+
+    fn closed(self: &Self) -> bool {
+        self.file.is_none()
+    }
+}
+
+fn main() -> io::Result<()> {
+    let mut fm = FileManager::new("test.txt", 'w');
+    fm.with(|f| -> io::Result<()> {
+        f.write(b"Test")?;
+        Ok(())
+    })?;
+    println!("{}", fm.closed());
+    Ok(())
+}
