# How to modify a JSON object that's been read in?
**URL:** https://discourse.julialang.org/t/how-to-modify-a-json-object-thats-been-read-in/68775
**Category:** Data
**Created:** [September 26, 2021, 1:15pm UTC](https://discourse.julialang.org/t/how-to-modify-a-json-object-thats-been-read-in/68775 "2021-09-26T13:15:16Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [September 26, 2021, 1:15pm UTC](https://discourse.julialang.org/t/how-to-modify-a-json-object-thats-been-read-in/68775/1 "2021-09-26T13:15:16Z")
I have read a JSON using JSON3.jl but after that I can’t seem to modify the json.
E.g.
```julia
a = JSON3.read("{\"a\":1}")
a[:b] = 2
```
what I get is this.
Is there an easy to mutate the object?
```julia
LoadError: MethodError: no method matching setindex!(::JSON3.Object{Base.CodeUnits{UInt8, String}, Vector{UInt64}}, ::Int64, ::Symbol)
e[0mClosest candidates are:
e[0m setindex!(::AbstractDict, ::Any, ::Any, e[91m::Anye[39m, e[91m::Any...e[39m) at abstractdict.jl:505
MethodError: no method matching setindex!(::JSON3.Object{Base.CodeUnits{UInt8, String}, Vector{UInt64}}, ::Int64, ::Symbol)
Closest candidates are:
setindex!(::AbstractDict, ::Any, ::Any, ::Any, ::Any...) at abstractdict.jl:505
Stacktrace:
[1] top-level scope
@ In[139]:3
[2] eval
@ ./boot.jl:360 [inlined]
[3] include_string(mapexpr::typeof(REPL.softscope), mod::Module, code::String, filename::String)
@ Base ./loading.jl:1094
```
---
### Author:  [@pfitzseb](https://discourse.julialang.org/u/pfitzseb)
#### Post date: [September 26, 2021, 1:53pm UTC](https://discourse.julialang.org/t/how-to-modify-a-json-object-thats-been-read-in/68775/2 "2021-09-26T13:53:58Z")
As per the [docs](https://quinnj.github.io/JSON3.jl/stable/#Builtin-types):
> The `JSON3.Object` supports the `AbstractDict` interface, but is read-only (it represents a _view_ into the JSON source input), thus it supports `obj[:x]` and `obj["x"]` , as well as `obj.x` for accessing fields. It supports `keys(obj)` to see available keys in the object structure. You can call `length(obj)` to see how many key-value pairs there are, and it iterates `(k, v)` pairs like a normal `Dict` . It also supports the regular `get(obj, key, default)` family of methods.
>
> The `JSON3.Array{T}` supports the `AbstractArray` interface, but like `JSON3.Object` is a _view_ into the input JSON, hence is read-only. It supports normal array methods like `length(A)` , `size(A)` , iteration, and `A[i]` `getindex` methods.
>
> If you really need `Dict` s and `Vector` s, then you can use `copy(x)` to recursively convert `JSON3.Object` s to `Dict` s and `JSON3.Array` s to `Vector` s.
---
### Author:  [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [September 27, 2021, 1:04am UTC](https://discourse.julialang.org/t/how-to-modify-a-json-object-thats-been-read-in/68775/3 "2021-09-27T01:04:45Z")
Just use `copy` to turn it into something mutable
```julia
using JSON3
a = JSON3.read("{\"a\":1}")
a = copy(a)
a[:b] = 2
```