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The Go Programming Language
book

The Go Programming Language

by Alan A. A. Donovan, Brian W. Kernighan
October 2015
Beginner to intermediate content levelBeginner to intermediate
400 pages
14h 44m
English
Addison-Wesley Professional
Content preview from The Go Programming Language

7.3 Interface Satisfaction

A type satisfies an interface if it possesses all the methods the interface requires. For example, an *os.File satisfies io.Reader, Writer, Closer, and ReadWriter. A *bytes.Buffer satisfies Reader, Writer, and ReadWriter, but does not satisfy Closer because it does not have a Close method. As a shorthand, Go programmers often say that a concrete type “is a” particular interface type, meaning that it satisfies the interface. For example, a *bytes.Buffer is an io.Writer; an *os.File is an io.ReadWriter.

The assignability rule (§2.4.2) for interfaces is very simple: an expression may be assigned to an interface only if its type satisfies the interface. So:

var w io.Writer w = os.Stdout ...
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Publisher Resources

ISBN: 9780134190570Purchase book