一路跟过来的，必须手动将之后例子的代码放入一个 main 函数中。这样，例子将显得更加简 明，使我们可以关注实际细节而不是样板代码。 在所有权的第一个例子中，我们看看一些变量的 作用域（scope）。作用域是一个项（item） 在程序中有效的范围。假设有这样一个变量： let s = "hello"; 变量 s 绑定到了一个字符串字面值，这个字符串值是硬编码进程序代码中的。这个变量从声明 的点开始直到当前作用域结束时都是有效的。示例 量离开作用域，Rust 为我们调用一个特殊的函数。这个函数叫做 drop，在这里 String 的作 者可以放置释放内存的代码。Rust 在结尾的 } 处自动调用 drop。 注意：在 C++ 中，这种 item 在生命周期结束时释放资源的模式有时被称作 资源获取 即初始化（Resource Acquisition Is Initialization (RAII)）。如果你使用过 RAII 模式的 话应该对 first_word(s: &String) -> usize { let bytes = s.as_bytes(); for (i, &item) in bytes.iter().enumerate() { if item == b' ' { return i; } } s.len() } 示例 4-7：first_word

Queue.get pauses until there is an item in the queue. If the queue has a maximum size set, a coroutine that yields Queue.put pauses until there is room for another item. A Queue maintains a count of unfinished markup:

{% for item in items %}
• {{ escape(item) }}
{% end %}

If you saved this template as “template template with: class MainHandler(tornado.web.RequestHandler): def get(self): items = ["Item 1", "Item 2", "Item 3"] self.render("template.html", title="My title", items=items) Tornado templates support

Queue.get pauses until there is an item in the queue. If the queue has a maximum size set, a coroutine that yields Queue.put pauses until there is room for another item. A Queue maintains a count of unfinished

{% for item in items %}
• {{ escape(item) }}
{% end %}

If you saved this template with: class MainHandler(tornado.web.RequestHandler): def get(self): items = ["Item 1", "Item 2", "Item 3"] self.render("template.html", title="My title", items=items) Tornado templates

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing (item, state) = next # body next = iterate(iter

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing (item, state) = next # body next = iterate(iter

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain rely upon iteration. It can also be used directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain rely upon iteration. It can also be used directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain rely upon iteration. It can also be used directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain rely upon iteration. It can also be used directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing

hexadecimal literals, binary and octal literals produce unsigned integer types. The size of the binary data item is the minimal needed size, if the leading digit of the literal is not 0. In the case of leading zeros iterate(iter) Returns either a tuple of the first item and initial state or nothing if empty iterate(iter, state) Returns either a tuple of the next item and next state or nothing if no items remain rely upon iteration. It can also be used directly in a for loop since the syntax: for item in iter # or "for item = iter" # body end is translated into: next = iterate(iter) while next !== nothing