pub struct Reference { /* private fields */ }Expand description
Represents an attribute name or path expression identifying a value within a crate::Context.
This can be used to retrieve a value with crate::Context::get_value, or to identify an attribute or nested value that should be considered private with crate::ContextBuilder::add_private_attribute (the SDK configuration can also have a list of private attribute references).
This is represented as a separate type, rather than just a string, so that validation and parsing can be done ahead of time if an attribute reference will be used repeatedly later (such as in flag evaluations).
If the string starts with ‘/’, then this is treated as a slash-delimited path reference where the first component is the name of an attribute, and subsequent components are the names of nested JSON object properties. In this syntax, the escape sequences “~0” and “~1” represent ‘~’ and ‘/’ respectively within a path component.
If the string does not start with ‘/’, then it is treated as the literal name of an attribute.
Example
// Given the following JSON representation of a context:
{
"kind": "user",
"key": "123",
"name": "xyz",
"address": {
"street": "99 Main St.",
"city": "Westview"
},
"a/b": "ok"
}
assert_eq!(context.get_value(&Reference::new("name")),
Some(AttributeValue::String("xyz".to_owned())));
assert_eq!(context.get_value(&Reference::new("/address/street")),
Some(AttributeValue::String("99 Main St.".to_owned())));
assert_eq!(context.get_value(&Reference::new("a/b")),
Some(AttributeValue::String("ok".to_owned())));
assert_eq!(context.get_value(&Reference::new("/a~1b")),
Some(AttributeValue::String("ok".to_owned())));Implementations§
source§impl Reference
impl Reference
sourcepub fn new<S: AsRef<str>>(value: S) -> Self
pub fn new<S: AsRef<str>>(value: S) -> Self
Construct a new context attribute reference.
This constructor always returns a reference that preserves the original string, even if validation fails, so that serializing the reference to JSON will produce the original string.
sourcepub fn error(&self) -> String
pub fn error(&self) -> String
If the reference is invalid, this method returns an error description; otherwise, it returns an empty string.
sourcepub fn depth(&self) -> usize
pub fn depth(&self) -> usize
Returns the number of path components in the reference.
For a simple attribute reference such as “name” with no leading slash, this returns 1.
For an attribute reference with a leading slash, it is the number of slash-delimited path components after the initial slash.
Example
assert_eq!(Reference::new("a").depth(), 1);
assert_eq!(Reference::new("/a/b").depth(), 2);sourcepub fn component(&self, index: usize) -> Option<&str>
pub fn component(&self, index: usize) -> Option<&str>
Retrieves a single path component from the attribute reference.
Returns the attribute name for a simple attribute reference such as “name” with no leading slash, if index is zero.
Returns the specified path component if index is less than Reference::depth, and the reference begins with a slash.
If index is out of range, it returns None.
Examples
assert_eq!(Reference::new("a").component(0), Some("a"));
assert_eq!(Reference::new("/a/b").component(1), Some("b"));
assert_eq!(Reference::new("/a/b").component(2), None);