What is the usage of backtick in golang structs definition?
GoGo Problem Overview
type NetworkInterface struct {
Gateway string `json:"gateway"`
IPAddress string `json:"ip"`
IPPrefixLen int `json:"ip_prefix_len"`
MacAddress string `json:"mac"`
...
}
I'm quite confused what's the function of contents in backtick, like json:"gateway"
.
Is it just comment, like //this is the gateway
?
Go Solutions
Solution 1 - Go
The content inside the backticks are tags:
> A field declaration may be followed by an optional string literal tag, > which becomes an attribute for all the fields in the corresponding > field declaration. The tags are made visible through a reflection > interface and take part in type identity for structs but are otherwise > ignored. > > // A struct corresponding to the TimeStamp protocol buffer. > // The tag strings define the protocol buffer field numbers. > struct { > microsec uint64 "field 1" > serverIP6 uint64 "field 2" > process string "field 3" > }
See this question and answer for a more detailed explanation and answer.
The back quotes are used to create raw string literals which can contain any type of character:
> Raw string literals are character sequences between back quotes ``. > Within the quotes, any character is legal except back quote.
Solution 2 - Go
You can add extra meta information to Go structs in the form of tags. Here are some examples of use cases.
In this case, the json:"gateway"
is used by the json package to encode the value of Gateway
into the key gateway
in the corresponding json object.
Example:
n := NetworkInterface{
Gateway : "foo"
}
json.Marshal(n)
// will output `{"gateway":"foo",...}`