Setting value to named field in Julia – setfield() Method

The setfield() is an inbuilt function in julia which is used to assign a value x to a named field in value of composite type. The value must be mutable and x must be a subtype of fieldtype(typeof(value), name)

Syntax:

setfield(value, name::Symbol, x)

Parameters:

• value: Specified value of composite type.
• name::Symbol: Specified symbol.
• x: Specified value.

Returns: It returns the assigned value x to a named field in value of composite type. 

Example 1:

Python

# Julia program to illustrate
# the use of setfield() method

# Getting the assigned value 'x' to
# a named field in value of composite type.
mutable struct MyMutableStruct
           field::Int
       end

a = MyMutableStruct(1);
setfield (a, :field, 123);
println(getfield(a, :field))

Output:

123

Example 2:

Python

# Julia program to illustrate
# the use of setfield() method

# Getting the assigned value 'x' to
# a named field in value of composite type.
a = 5//3
println(setfield (a, :num, 123))

Output:

ERROR: LoadError: type Rational is immutable
while loading /home/cg/root/5090533/main.jl, in expression starting on line 7