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codingStyleIdioms/3_RAII/RAII_fstram.cpp

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+//
+// Created by light on 19-12-9.
+//
+#include <iostream>
+#include <fstream>
+
+// RAII 资源获取即初始化,例2
+
+// C ++保证在对象超出范围时调用析构函数，而不管控制如何离开该范围。
+// 即使抛出异常，所有本地对象也会超出范围，因此它们的相关资源将被清除。
+
+void foo() {
+    std::fstream file("bar.txt"); // open a file "bar.txt"
+    if (rand() % 2) {
+        // if this exception is thrown, we leave the function, and so
+        // file's destructor is called, which closes the file handle.
+        throw std::exception();
+    }
+    // if the exception is not called, we leave the function normally, and so
+    // again, file's destructor is called, which closes the file handle.
+}
+
+int main() {
+    try {
+        foo();
+    } catch (std::exception) {
+        puts("exception!");
+    }
+}