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Generated Files

  • The constants.go file, which contains all constants.

  • The ttypes.go, which contains type definitions.

$ tree gen-go
`-- thrift
    `-- example
        |-- constants.go
        `-- ttypes.go
Tip
Naming with Go

The Go language uses capitalization to determine export rules. The Go thrift library adapts thrift names to adhere to this convention. So a struct field called userName will be accessible in Go as UserName. As a rule, the first letter of any constant or struct field will be capitalized.

Types

Thrift maps the various base and container types to Go types as follows:

  • bool: bool

  • binary: []byte

  • byte: byte

  • i16: int16

  • i32: int32

  • i64: int64

  • double: float64

  • string: string

  • list<t1>: []t1

  • set<t1>: map[t1]bool where bool is always true

  • map<t1,t2>: map[t1]t2

With the exception of set, which has no direct Go equivalent, all of the types are straightforward.

The Thrift developers decided that the best way to represent Thrift set types in Go was to implement them as map[t1]bool.

Typedefs

Thrift typedefs are implemented in Go as Go types. Thus typedef i32 MyInt becomes the Go type MyInt int32.

Enums

The Go Thrift compiler translates enums to constants. The strategy it employs is to create a set of constants where the enum name is the prefix and the enum item’s name is the suffix. The two are separated by an underscore (_).

The TweetType of TWEET becomes, in Go, TweetType_TWEET.

Constants

Thrift constants are declared const for Go types that can be declared as constants (e.g. int, string, etc.). For types that cannot be declared const (like maps and slices), the Go library declares these as global var.

Structs

The Thrift struct is translated to Go struct differently than in other language libraries.

Unlike most Thrift implementations, the type declarations are substantially impacted by whether or not a thrift attribute is declared required or optional. To distinguish between an empty value and a nil value, the Go library uses pointers for all optional values.

For example, here is an abbreviated listing of the Tweet struct discussed above:

struct Tweet {
  1: required i32 userId
  // ...
  4: optional Location loc
  // ...
}

In Go, the field userId will be UserId int32, while loc will be Loc *Location. The salient detail is that any field tagged as optional will be implemented as a Go pointer to a value, while required types are implemented as values.

Unions

Thrift union types are translated into Go structs, where only one field on the struct may be set to a non-nil value.