README
¶
Weld
Weld is a golang package that contains directives for Luno style "state and backends" dependency injection using compile time code generation.
Weld is heavily based on wire (github.com/google/wire), borrowing its syntax and concepts but tailoring it for Luno's specific state and backends based dependency injection pattern. Unlike wire, weld supports multiple providers for the same type by selecting the first provider found in the set using depth first search. Unlike wire, weld also supports transitive "backends-type" cyclic dependencies by adding these interfaces to the generated implementation.
Unlike wire, weld is much less dynamic with fewer features, it takes a provider set as input and a backends as output and generates a Make function that returns an implementation of that backends interface.
For convenience it can also generate an aggregate Backends interface from the union of a slice of backends since golang doesn't support embedding interfaces with the same name or overlapping methods.
Relation to wire syntax:
- Supported functions and types: wire.NewSet, wire.ProviderSet, wire.Bind, wire.Binding.
- Unsupported functions and types: wire.Build, wire.Struct, wire.FieldsOf, wire.Value, wire.InterfaceValue.
See the internal/testdata/example project for how this is used.
For more details, see the weld godoc.
Documentation
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Overview ¶
Package weld contains directives for Luno style state and backends dependency injection using compile time code generation.
Weld is heavily based on wire (github.com/google/wire), borrowing its syntax and concepts but tailoring it for Luno's specific state and backends based dependency injection pattern. Unlike wire, weld supports multiple providers for the same type by selecting the first provider found in the set using depth first search. Unlike wire, weld also supports transitive "backends-type" cyclic dependencies by adding these interfaces to the generated implementation.
Unlike wire, weld is much less dynamic with fewer features, it takes a provider set as input and a backends as output and generates a Make function that returns an implementation of that backends interface.
For convenience it can also generate an aggregate Backends interface from the union of a slice of backends since golang doesn't support embedding interfaces with the same name or overlapping methods.
Relation to wire syntax:
Supported functions and types: wire.NewSet, wire.ProviderSet, wire.Bind, wire.Binding. Unsupported functions and types: wire.Build, wire.Struct, wire.FieldsOf, wire.Value, wire.InterfaceValue.
See the internal/testdata/example project for how this is used.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func NewSpec ¶
func NewSpec(set ProviderSet, backends Backends) string
NewSpec creates a weld specification that can generate a Make function for a backends interface from the provider set. The backends interface is a Luno style dependency provider interface with only pure getters.
Note that NewSpec is not a wire concept, but it could be seen as replacing the wire.Build function.
Given a spec, the weld command will generate a weld_gen.go file.
Example:
//go:build weld package state import ( ... ) //go:generate weld var _ = weld.NewSpec( weld.NewSet(provider.WeldProd), weld.GenUnion(new(exchange_ops.Backends), new(matcher_ops.Backends))
Or for an alternative dev environment state:
var _ = weld.NewSpec( weld.NewSet(provider.WeldDev), weld.Existing(new(state.Backends))
Types ¶
type Backends ¶
type Backends struct{}
Backends is a marker type of the resulting generated backends interface; basically the output of weld.
Note that Backends is not a wire concept.
func Existing ¶
func Existing(backends interface{}) Backends
Existing specifies that a single existing backends interface be used as output of weld.
Note that Existing is not a wire concept.
Example:
var _ = weld.NewSpec(
providers.WeldDev,
weld.Existing(new(state.Backends))
func GenUnion ¶
func GenUnion(backends ...interface{}) Backends
GenUnion specifies that a new backends interface must be generated that is the union of the all the provided backends interfaces.
Note that GenUnion is not a wire concept.
Example:
var _ = weld.NewSpec(
providers.WeldProd,
weld.GenUnion(new(exchange_ops.Backends), new(matcher_ops.Backends))
type Binding ¶
type Binding struct{}
Binding maps an interface to a concrete type.
This type is heavily based on github.com/google/wire.Binding, see it for more details.
func Bind ¶
func Bind(iface, to interface{}) Binding
Bind declares that a concrete type should be used to satisfy a dependency on the type of iface. iface must be a pointer to an interface type, to must be a pointer to a concrete type.
This type is heavily based on github.com/google/wire.Bind, see it for more details.
Example:
type Client interface {
List()
}
func New() *client {...}
type client struct{}
func (*client) List() {}
var Provider = weld.NewSet(New, weld.Bind(new(Client), new(*client)))
type ProviderSet ¶
type ProviderSet struct{}
ProviderSet is a marker type that collects a group of providers.
This type is heavily based on github.com/google/wire.ProviderSet, see it for more details.
func NewSet ¶
func NewSet(...interface{}) ProviderSet
NewSet creates a new provider set that includes the providers in its arguments. Each argument is a function value, a provider set or a call to Bind.
This type is heavily based on github.com/google/wire.NewSet, see it for more details.
Source Files
Directories