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package dynamodb
import simplejson "github.com/bitly/go-simplejson"
/*
Construct an update item query.
The query can be composed via chaining and then executed via Execute()
Usage:
update := table.UpdateItem(key)
.ReturnValues(dynamodb.UPDATED_NEW)
.UpdateExpression("SET Counter = Counter + :incr")
.UpdateCondition("Counter < :checkVal")
.ExpressionAttributes(NewNumberAttribute(":incr", "1"), NewNumberAttribute(":checkVal", 42))
result, err := update.Execute()
if err == nil {
log.Printf("Counter is now %v", result.Attributes["Counter"].Value)
}
*/
func (t *Table) UpdateItem(key *Key) *UpdateItem {
q := NewQuery(t)
q.AddKey(t, key)
return &UpdateItem{table: t, query: q}
}
type UpdateItem struct {
table *Table
query *Query
hasReturnValues bool
}
// Specify how return values are to be provided.
func (u *UpdateItem) ReturnValues(returnValues ReturnValues) *UpdateItem {
u.hasReturnValues = (returnValues != NONE)
u.query.AddReturnValues(returnValues)
return u
}
/*
Specify an update expression and optional attribute settings at the same time.
update.UpdateExpression("SET Foo = Foo + :incr", dynamodb.NewNumberAttribute(":incr", "7"))
is equivalent to
update.UpdateExpression("SET Foo = Foo + :incr")
.ExpressionAttributes(NewNumberAttribute(":incr", "7"))
*/
func (u *UpdateItem) UpdateExpression(expression string, attributes ...Attribute) *UpdateItem {
u.query.AddUpdateExpression(expression)
u.ExpressionAttributes(attributes...)
return u
}
// Specify attribute substitutions to be used in expressions.
func (u *UpdateItem) ExpressionAttributes(attributes ...Attribute) *UpdateItem {
u.query.AddExpressionAttributes(attributes)
return u
}
// Specify a check condition for conditional updates.
func (u *UpdateItem) ConditionExpression(expression string) *UpdateItem {
u.query.AddConditionExpression(expression)
return u
}
// Execute this query.
func (u *UpdateItem) Execute() (*UpdateResult, error) {
jsonResponse, err := u.table.Server.queryServer(target("UpdateItem"), u.query)
if err != nil {
return nil, err
}
if u.hasReturnValues {
resp, err := simplejson.NewJson(jsonResponse)
if err != nil {
return nil, err
}
attrib, err := resp.Get("Attributes").Map()
if err != nil {
return nil, err
}
return &UpdateResult{parseAttributes(attrib)}, nil
}
return nil, nil
}
type UpdateResult struct {
Attributes map[string]*Attribute
}
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