diff options
Diffstat (limited to 'vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go')
| -rw-r--r-- | vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go | 67 |
1 files changed, 45 insertions, 22 deletions
diff --git a/vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go b/vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go index 978511cbfa..c1e20f9489 100644 --- a/vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go +++ b/vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/doc.go @@ -27,28 +27,51 @@ // // Registry and RegistryBuilder // -// A Registry is an immutable store for ValueEncoders, ValueDecoders, and a type map. For looking up -// ValueEncoders and Decoders the Registry first attempts to find a ValueEncoder or ValueDecoder for -// the type provided; if one cannot be found it then checks to see if a registered ValueEncoder or -// ValueDecoder exists for an interface the type implements. Finally, the reflect.Kind of the type -// is used to lookup a default ValueEncoder or ValueDecoder for that kind. If no ValueEncoder or -// ValueDecoder can be found, an error is returned. -// -// The Registry also holds a type map. This allows users to retrieve the Go type that should be used -// when decoding a BSON value into an empty interface. This is primarily only used for the empty -// interface ValueDecoder. -// -// A RegistryBuilder is used to construct a Registry. The Register methods are used to associate -// either a reflect.Type or a reflect.Kind with a ValueEncoder or ValueDecoder. A RegistryBuilder -// returned from NewRegistryBuilder contains no registered ValueEncoders nor ValueDecoders and -// contains an empty type map. -// -// The RegisterTypeMapEntry method handles associating a BSON type with a Go type. For example, if -// you want to decode BSON int64 and int32 values into Go int instances, you would do the following: -// -// var regbuilder *RegistryBuilder = ... intType := reflect.TypeOf(int(0)) -// regbuilder.RegisterTypeMapEntry(bsontype.Int64, intType).RegisterTypeMapEntry(bsontype.Int32, -// intType) +// A Registry is an immutable store for ValueEncoders, ValueDecoders, and a type map. See the Registry type +// documentation for examples of registering various custom encoders and decoders. A Registry can be constructed using a +// RegistryBuilder, which handles three main types of codecs: +// +// 1. Type encoders/decoders - These can be registered using the RegisterTypeEncoder and RegisterTypeDecoder methods. +// The registered codec will be invoked when encoding/decoding a value whose type matches the registered type exactly. +// If the registered type is an interface, the codec will be invoked when encoding or decoding values whose type is the +// interface, but not for values with concrete types that implement the interface. +// +// 2. Hook encoders/decoders - These can be registered using the RegisterHookEncoder and RegisterHookDecoder methods. +// These methods only accept interface types and the registered codecs will be invoked when encoding or decoding values +// whose types implement the interface. An example of a hook defined by the driver is bson.Marshaler. The driver will +// call the MarshalBSON method for any value whose type implements bson.Marshaler, regardless of the value's concrete +// type. +// +// 3. Type map entries - This can be used to associate a BSON type with a Go type. These type associations are used when +// decoding into a bson.D/bson.M or a struct field of type interface{}. For example, by default, BSON int32 and int64 +// values decode as Go int32 and int64 instances, respectively, when decoding into a bson.D. The following code would +// change the behavior so these values decode as Go int instances instead: +// +// intType := reflect.TypeOf(int(0)) +// registryBuilder.RegisterTypeMapEntry(bsontype.Int32, intType).RegisterTypeMapEntry(bsontype.Int64, intType) +// +// 4. Kind encoder/decoders - These can be registered using the RegisterDefaultEncoder and RegisterDefaultDecoder +// methods. The registered codec will be invoked when encoding or decoding values whose reflect.Kind matches the +// registered reflect.Kind as long as the value's type doesn't match a registered type or hook encoder/decoder first. +// These methods should be used to change the behavior for all values for a specific kind. +// +// Registry Lookup Procedure +// +// When looking up an encoder in a Registry, the precedence rules are as follows: +// +// 1. A type encoder registered for the exact type of the value. +// +// 2. A hook encoder registered for an interface that is implemented by the value or by a pointer to the value. If the +// value matches multiple hooks (e.g. the type implements bsoncodec.Marshaler and bsoncodec.ValueMarshaler), the first +// one registered will be selected. Note that registries constructed using bson.NewRegistryBuilder have driver-defined +// hooks registered for the bsoncodec.Marshaler, bsoncodec.ValueMarshaler, and bsoncodec.Proxy interfaces, so those +// will take precedence over any new hooks. +// +// 3. A kind encoder registered for the value's kind. +// +// If all of these lookups fail to find an encoder, an error of type ErrNoEncoder is returned. The same precedence +// rules apply for decoders, with the exception that an error of type ErrNoDecoder will be returned if no decoder is +// found. // // DefaultValueEncoders and DefaultValueDecoders // |