json/features/element_access.md

Element Access

There are many ways elements in a JSON value can be accessed:

• unchecked access via operator[]
• checked access via at
• access with default value via value
• iterators
• JSON pointers

Testing whether a key or index exists before accessing it is also possible, with contains or find (which returns an iterator to the value, or end() if it is not found).

flowchart TD
    A["accessing a value"] --> B{"must it exist?"}
    B -->|"yes, missing is an error"| C["at() -- throws"]
    B -->|"yes, but checking is my job"| D["operator[] -- unchecked"]
    B -->|"no, a fallback is fine"| E["value() -- default value"]
    A --> F{"just testing first?"}
    F -->|"yes"| G["contains() / find()"]