<p>for example, I want to assign the variable only the condition met</p>
<pre><code>if cond {
foo := func
}
// use foo, but it's out of scope
</code></pre>
<hr/>**评论：**<br/><br/>_jenni4: <pre><p>In most cases you can think of curly braces as "define a separate scope, here."</p>
<p>Information from nested scopes can't be accessed by enclosing scopes, but can go the other way.</p>
<p>Example: <a href="https://play.golang.org/p/B9eEPyveK0h" rel="nofollow">https://play.golang.org/p/B9eEPyveK0h</a></p></pre>sharptoothy: <pre><p>Perhaps I just don't get something but why not just say:</p>
<pre><code>if cond {
v := someFunc()
// use v here
}
// don't use v here
</code></pre>
<p>Unless v was already defined somewhere else and just might need to be updated:</p>
<pre><code>func (o obj) getValue(a int) int {
if o.needsUpdate() {
a = o.updatedInt()
}
return o.doSomething(a)
}
</code></pre>
<p>Or you're doing something like what 014a said where in an else branch, you want to set the value to something else. Is there some other situation?</p></pre>014a: <pre><p>I write code with this general logic quite often.</p>
<pre><code>if cond {
foo = Thing()
} else {
foo = OtherThing()
}
</code></pre>
<p>The easiest way to accomplish this similarly in Go is to define the variable before the branches</p>
<pre><code>var foo Bar
if cond {
...
</code></pre>
<p>It works and is a good pattern. The other thing you can do, which might be cleaner depending on your specific logic, is to use an anonymous function:</p>
<pre><code>foo := func() Bar {
if cond {
return Thing()
} else {
return OtherThing()
}
}()
</code></pre>
<p>And depending on the size of each branch you may want to break that out into its own separate function.</p></pre>hell_0n_wheel: <pre><blockquote>
<p>use an anonymous function:</p>
</blockquote>
<p>Especially if you need to populate the value from an external source. I use this pattern often:</p>
<pre><code>err := func(*s SomeType) error {
c := NewClient(dbconn)
defer c.Close()
s, err := c.Get()
return err
}()
</code></pre>
<p>The anon function traps the scope of the defer statement, so you can use multiple clients in the same method... if that's your cuppa tea.</p></pre>a_t-2: <pre><pre><code> var foo type
if cond {
foo = value
}
// use foo
</code></pre>
<p>A language has rules, you can't just make up new ones because you don't like them.</p></pre>
