# How to make dict lookups work with an overloaded == and hash function
**URL:** https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098
**Category:** New to Julia
**Created:** [October 1, 2022, 10:24pm UTC](https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098 "2022-10-01T22:24:30Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@ivoytov](https://discourse.julialang.org/u/ivoytov)
#### Post date: [October 1, 2022, 10:24pm UTC](https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098/1 "2022-10-01T22:24:30Z")
I have a custom type that includes a string as it’s unique ID. I would like to simplify operations by permitting lookups of this object by just the String. I proceed with the basic construction and of course it doesn’t work by default.
```julia
julia> struct MyString
name::String
end
julia> a = MyString("Ilya")
MyString("Ilya")
julia> d = Dict{MyString,Integer}()
Dict{MyString, Integer}()
julia> d[a] = 1
1
julia> d["Ilya"]
ERROR: KeyError: key "Ilya" not found
```
Easy, I’ll overload equals and everything should be dandy:
```julia
julia> import Base: ==
julia> ==(x::MyString, y::String) = x.name == y
== (generic function with 225 methods)
julia> a == "Ilya"
true
julia> d["Ilya"]
ERROR: KeyError: key "Ilya" not found
```
Hmm, maybe I need to overload hash() as well?
```julia
julia> import Base: hash
julia> hash(mys::MyString) = hash(mys.name)
hash (generic function with 88 methods)
julia> d["Ilya"]
ERROR: KeyError: key "Ilya" not found
```
So I was pretty stumped at this point, but then I tried overloading `==(x::String, y::MyString) = x == y.name` and everything worked beautifully.
My question is what is the correct way to implement this behavior? Do I need to overload all three functions or can I get away with just one?
---
### Author:  [@Oscar\_Smith](https://discourse.julialang.org/u/Oscar_Smith)
#### Post date: [October 1, 2022, 11:19pm UTC](https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098/2 "2022-10-01T23:19:55Z")
you need all three.
---
### Author:  [@ivoytov](https://discourse.julialang.org/u/ivoytov)
#### Post date: [October 2, 2022, 12:44am UTC](https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098/3 "2022-10-02T00:44:12Z")
so if I want to add `MyString` to sorted lists, do I also need to overload both `<` and `>`?
---
### Author:  [@Oscar\_Smith](https://discourse.julialang.org/u/Oscar_Smith)
#### Post date: [October 2, 2022, 12:51am UTC](https://discourse.julialang.org/t/how-to-make-dict-lookups-work-with-an-overloaded-and-hash-function/88098/4 "2022-10-02T00:51:37Z")
the docs for sorting specify that sorting uses `isless` (which falls back to `<`)