- 1 year ago
Setting a protobuf item's value replaces a previously set variable as well
If setting a value for a Protobuf item is replacing a previously set variable, it is likely due to the mutability behavior of the Protobuf library. Protobuf objects are designed to be immutable by default, which means that setting a value on one field will create a new instance of the object with the updated value, rather than modifying the existing object.
To avoid overwriting previously set values, you need to ensure that you are working with the same instance of the Protobuf object throughout your code. Here are a few guidelines to follow:
Retrieve the Protobuf object from its parent message: When working with nested Protobuf messages, make sure you retrieve the child object from its parent message using the appropriate accessor method. This ensures that you are working with the same instance of the object and can modify its values without overwriting previous assignments.
Avoid reassigning the Protobuf object: Instead of assigning a new instance of the Protobuf object to a variable, use the existing instance and modify its properties directly. Reassigning a new instance will lose any previous values.
Incorrect:
pythonmy_message = MyMessage()
my_message.field = "Value 1"
my_message = MyMessage() # This creates a new instance
my_message.field = "Value 2" # Overwrites previous value
Correct:
pythonmy_message = MyMessage()
my_message.field = "Value 1"
my_message.field = "Value 2" # Updates the existing instance
Use repeated fields for multiple values: If you need to store multiple values for a field, make sure the field is defined as a repeated field in your Protobuf message definition. This allows you to add multiple values to the same field without overwriting previous entries.
Protobuf message definition:
cmessage MyMessage {
repeated string field = 1;
}
Usage:
pythonmy_message = MyMessage()
my_message.field.append("Value 1")
my_message.field.append("Value 2")
By following these guidelines, you should be able to set values on Protobuf items without inadvertently replacing previously set variables. Remember to consult the Protobuf documentation and follow best practices specific to the programming language you are using.