getfield

getfield(value, name::Symbol)

Extract a named field from a value of composite type. The syntax a.b calls getfield(a, :b), and the syntax a.(b) calls getfield(a, b).

Examples

In the Julia programming language, the function getfield(value, name::Symbol)

Extracts a named field from a value of composite type. The syntax a.b calls getfield(a, :b), and the syntax a.(b) calls getfield(a, b).

Here are some common examples of how to use getfield:

Access a field from a struct:

julia> struct Person
          name::String
          age::Int
      end

julia> p = Person("Alice", 25)
Person("Alice", 25)

julia> getfield(p, :name)
"Alice"

This example shows how to access the name field of a Person struct using getfield.

Access a nested field from a nested struct:

julia> struct Address
          street::String
          city::String
      end

julia> struct Person
          name::String
          age::Int
          address::Address
      end

julia> p = Person("Bob", 30, Address("123 Main St", "New York"))

julia> getfield(getfield(p, :address), :street)
"123 Main St"

In this example, we access the nested street field of the address field within the Person struct.

Use dot syntax for field access:

julia> struct Point
          x::Float64
          y::Float64
      end

julia> p = Point(3.5, 2.0)

julia> p.x
3.5

julia> getfield(p, :x)
3.5

The dot syntax p.x is equivalent to getfield(p, :x). Both methods access the x field of the Point struct.

Common mistake example:

julia> struct Rectangle
           width::Float64
           height::Float64
       end

julia> r = Rectangle(5.0, 3.0)

julia> getfield(r, "width")
ERROR: MethodError: no method matching getfield(::Rectangle, ::String)

In this example, the field name is passed as a string instead of a symbol. The correct usage is to pass the field name as a symbol (:width) to getfield.

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getfield

Examples

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