Twig: how to add an object into multi level object - twig

Question

In twig template I have an object with multiple levels
I need to add a new object into the multiple object as the sub object
{%
set data = {
'first': 'First',
'data': {
'val_1': 'val_1'
}
}
%}
this should be added to data val_2: val_2
expected result:
{%
set data = {
'first': 'First',
'data': {
'val_1': 'val_1',
'val_2': 'val_2'
}
}
%}

Answer 1

First, in Twig terminology, that's not an object or a key-value array but a hash (see Twig's documentation of literals).
You can't add an item to a hash e.g. by doing {% set data.second = 'Second' %}. Instead you need to use the merge filter:
{%
set data = data|merge({
second: 'Second',
})
%}
{{ dump(data) }}
{# Prints this:
array(3) {
["first"]=>
string(5) "First"
["data"]=>
array(1) {
["val_1"]=>
string(5) "val_1"
}
["second"]=>
string(6) "Second"
}
#}
So, to add an item to a hash inside a hash, you need to use the merge filter twice:
{%
set data = data|merge({
data: data.data|merge({
val_2: 'val_2',
}),
})
%}
{# Prints this:
array(3) {
["first"]=>
string(5) "First"
["data"]=>
array(1) {
["val_1"]=>
string(5) "val_1"
["val_2"]=>
string(5) "val_2"
}
["second"]=>
string(6) "Second"
}
#}
If you do lots of this kind of variable manipulation in Twig, it might be a sign that some of that code might be better put in a controller or model or whatever.