<p>hey folks newbie question here but in the code <a href="https://play.golang.org/p/5CNdVb1DXL" rel="nofollow">https://play.golang.org/p/5CNdVb1DXL</a> since Cache is an interface and MemoryCache is an implementation of that why can I not assign "TheCache = NewMemoryCache()" and how should I go about that - thank you!!!</p>
<hr/>**评论：**<br/><br/>sharptierce: <pre><p>There are two ways here:
<a href="https://play.golang.org/p/n6O6V5lzu-" rel="nofollow">https://play.golang.org/p/n6O6V5lzu-</a>
since Get only reads the pointer is not necessary.</p>
<p>The other solution would be:
<a href="https://play.golang.org/p/Owg-U_JYsk" rel="nofollow">https://play.golang.org/p/Owg-U_JYsk</a>
where you take the pointer to the object and now it implements the interface.</p>
<p>Kinda hard at the beginning to grasp :) </p></pre>runyoucleverboyrun: <pre><p>So how come there's a type problem when assigning a MemoryCache value to a Cache variable but not when assigning a MemoryCache pointer, and is the TheCache variable implicitly a pointer type or something?</p></pre>driusan: <pre><p>There's a type error when assigning a MemoryCache value because you didn't implement the interface on type MemoryCache, you implemented it on type *MemoryCache.</p></pre>sharptierce: <pre><p>if you define methods that have a pointer receiver they will only be implemented by pointers of the instance. Methods that have no pointe r receiver are implemented by both. </p>
<p>Methods with pointer receiver can manipulate the struct.</p>
<p>I'm bad at explaining though, you can read it up here <a href="https://golang.org/doc/faq#pointer_to_interface" rel="nofollow">https://golang.org/doc/faq#pointer_to_interface</a></p></pre>pafortin: <pre><p>thank you that was very helpful and got me unstuck!</p></pre>radovskyb: <pre><p>A more common approach would be to actually just return a pointer to a MemoryCache object from the NewMemoryCache() function in the first place: <a href="https://play.golang.org/p/rIe3y0viqx" rel="nofollow">https://play.golang.org/p/rIe3y0viqx</a></p></pre>binaryblade: <pre><p>Inorder for a value to satisfy an interface it must be a pointer if one of the method receivers required by the interface is a pointer. Its safe to automatically reduce to a value but not to take a pointer.</p></pre>
