AWSDynamoDBAttributeValueUpdate Class Reference
|Inherits from||AWSModel : AWSMTLModel|
UpdateItem operation, represents the attributes to be modified, the action to perform on each, and the new value for each.
You cannot use
UpdateItem to update any primary key attributes. Instead, you will need to delete the item, and then use
PutItem to create a new item with new attributes.
You cannot use
Attribute values cannot be null; string and binary type attributes must have lengths greater than zero; and set type attributes must not be empty. Requests with empty values will be rejected with a
Specifies how to perform the update. Valid values are
ADD. The behavior depends on whether the specified primary key already exists in the table.
If an item with the specified Key is found in the table:
PUT- Adds the specified attribute to the item. If the attribute already exists, it is replaced by the new value.
DELETE- If no value is specified, the attribute and its value are removed from the item. The data type of the specified value must match the existing value's data type.
If a set of values is specified, then those values are subtracted from the old set. For example, if the attribute value was the set
[a,c], then the final attribute value would be
[b]. Specifying an empty set is an error.
ADD- If the attribute does not already exist, then the attribute and its values are added to the item. If the attribute does exist, then the behavior of
ADDdepends on the data type of the attribute:
If the existing attribute is a number, and if
Valueis also a number, then the
Valueis mathematically added to the existing attribute. If
Valueis a negative number, then it is subtracted from the existing attribute.
If you use
ADDto increment or decrement a number value for an item that doesn't exist before the update, DynamoDB uses 0 as the initial value.
In addition, if you use
ADDto update an existing item, and intend to increment or decrement an attribute value which does not yet exist, DynamoDB uses
0as the initial value. For example, suppose that the item you want to update does not yet have an attribute named itemcount, but you decide to
3to this attribute anyway, even though it currently does not exist. DynamoDB will create the itemcount attribute, set its initial value to
0, and finally add
3to it. The result will be a new itemcount attribute in the item, with a value of
If the existing data type is a set, and if the
Valueis also a set, then the
Valueis added to the existing set. (This is a set operation, not mathematical addition.) For example, if the attribute value was the set
[1,2], and the
, then the final attribute value would be
[1,2,3]. An error occurs if an Add action is specified for a set attribute and the attribute type specified does not match the existing set type.
Both sets must have the same primitive data type. For example, if the existing data type is a set of strings, the
Valuemust also be a set of strings. The same holds true for number sets and binary sets.
This action is only valid for an existing attribute whose data type is number or is a set. Do not use
ADDfor any other data types.
If no item with the specified Key is found:
PUT- DynamoDB creates a new item with the specified primary key, and then adds the attribute.
DELETE- Nothing happens; there is no attribute to delete.
ADD- DynamoDB creates an item with the supplied primary key and number (or set of numbers) for the attribute value. The only data types allowed are number and number set; no other data types can be specified.
@property (nonatomic, assign) AWSDynamoDBAttributeAction action
Represents the data for an attribute.
Each attribute value is described as a name-value pair. The name is the data type, and the value is the data itself.
For more information, see Data Types in the Amazon DynamoDB Developer Guide.
@property (nonatomic, strong) AWSDynamoDBAttributeValue *value