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Column Resolvers

These types of resolvers are called for each row received in the TableResolver data fetch.

type ColumnResolver func(ctx context.Context, meta ClientMeta, resource *Resource, c Column) error

A ColumnResolver works by extracting data for the given Column from the given Resource, and setting it in the Resource using resource.Set():

func (r *Resource) Set(key string, value interface{}) error {

They usually go like:

func resolveDynamodbTableKeySchema(ctx context.Context, meta schema.ClientMeta, resource *schema.Resource, c schema.Column) error {
	r := resource.Item.(*types.TableDescription)
	value := marshalKeySchema(r.KeySchema)
	return resource.Set(c.Name, value)

This way, the value for the column c is extracted from the resource, marshalled, and set.

Utility Resolvers

Utility Resolvers provide solutions on converting data from one data structure to another, ready to be saved in tables. These are always of type ColumnResolver.

Some resolvers convert one type to another (parsing date fields, IP addresses and so on) and some look up data inside inner structs of a resource, or from the parent.


// Few examples of look-up helper resolvers:
// PathResolver resolves a field in the Resource.Item
func PathResolver(path string) ColumnResolver
// ParentResourceFieldResolver resolves a field from the parent's resource, the value is expected to be set, if name isn't set the field will be set to null
func ParentResourceFieldResolver(name string) ColumnResolver
// ParentPathResolver resolves a field from the parent
func ParentPathResolver(path string) ColumnResolver
// ParentIdResolver resolves the cq_id from the parent
func ParentIdResolver(_ context.Context, _ ClientMeta, r *Resource, c Column) error
// Few examples of type converting resolvers
// IntResolver tries to cast value into int
func IntResolver(path string) ColumnResolver
// DateResolver resolves the different date formats (ISODate - 2011-10-05T14:48:00.000Z is default) into *time.Time
func DateResolver(path string, rfcs ...string) ColumnResolver
// IPAddressResolver resolves the ip string value and returns net.IP
func IPAddressResolver(path string) ColumnResolver

Notice how most examples return an inline function built to resolve according to the given parameters (e.g. PathResolver will return a function that resolves for the given path) except for the ParentIdResolver, which is a static ColumnResolver.


Discover more ready-made utility resolvers in the repository.