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doc/effective_go: mention that b.Write is a shorthand for (&b).Write when b is addressable.

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The rewrite is due to Rob.

LGTM=r, bradfitz, josharian
R=golang-codereviews, bradfitz, r, josharian
CC=golang-codereviews
https://golang.org/cl/87410043
This commit is contained in:
Shenghou Ma 2014-04-17 01:40:04 -04:00
parent 827aab07b8
commit f8f34c330c
1 changed files with 15 additions and 3 deletions
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doc/effective_go.html
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@ -2056,10 +2056,22 @@ We pass the address of a <code>ByteSlice</code>
because only <code>*ByteSlice</code> satisfies <code>io.Writer</code>.
The rule about pointers vs. values for receivers is that value methods
can be invoked on pointers and values, but pointer methods can only be
invoked on pointers. This is because pointer methods can modify the
receiver; invoking them on a copy of the value would cause those
modifications to be discarded.
invoked on pointers.
</p>
<p>
This rule arises because pointer methods can modify the receiver; invoking
them on a value would cause the method to receive a copy of the value, so
any modifications would be discarded.
The language therefore disallows this mistake.
There is a handy exception, though. When the value is addressable, the
language takes care of the common case of invoking a pointer method on a
value by inserting the address operator automatically.
In our example, the variable <code>b</code> is addressable, so we can call
its <code>Write</code> method with just <code>b.Write</code>. The compiler
will rewrite that to <code>(&amp;b).Write</code> for us.
</p>
<p>
By the way, the idea of using <code>Write</code> on a slice of bytes
is central to the implementation of <code>bytes.Buffer</code>.