# Convert String to DataType
**URL:** https://discourse.julialang.org/t/convert-string-to-datatype/23803
**Category:** General Usage
**Created:** [May 3, 2019, 8:06am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803 "2019-05-03T08:06:39Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Eric\_Chen](https://discourse.julialang.org/u/Eric_Chen)
#### Post date: [May 3, 2019, 8:06am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/1 "2019-05-03T08:06:39Z")
I have a file that contains a List of what “Algo” I should run
Then Julia should read it and Create an instance of the correct “Algo” object:
```julia
abstract type OptimizationAlgo end
struct Linear <: OptimizationAlgo end
struct Quad <: OptimizationAlgo end
struct ThirdOrder <: OptimizationAlgo end
algo_str = readline() # Let's say I type in "Linear"
# Convert algo_str to the correct algo struct
# How to do it??
```
But how to efficiently do so?
The only way I could think of:
`@eval $(Symbol(algo_str))`
**Is there a way Without Using any Macro?**
---
### Author:  [@longemen3000](https://discourse.julialang.org/u/longemen3000)
#### Post date: [May 3, 2019, 8:14am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/2 "2019-05-03T08:14:07Z")
i can’t think of another solution of that other that a long function with a lot of ifs, maybe that is the correct approach, because the algorithm is not known a priori (before reading the file)
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### Author:  [@Eric\_Chen](https://discourse.julialang.org/u/Eric_Chen)
#### Post date: [May 3, 2019, 8:24am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/3 "2019-05-03T08:24:20Z")
Is there a way Without Using any Macro?
---
### Author:  [@carstenbauer](https://discourse.julialang.org/u/carstenbauer)
#### Post date: [May 3, 2019, 8:34am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/4 "2019-05-03T08:34:58Z")
If the number of algorithms is limited you can use a dictionary as a mapping from string to object.
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### Author:  [@tomaklutfu](https://discourse.julialang.org/u/tomaklutfu)
#### Post date: [May 3, 2019, 8:35am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/5 "2019-05-03T08:35:36Z")
You can short circuit equality for string such as
```julia
julia> algo_str = readline()
Linear
"Linear"
julia> algo_str == "Linear" && Linear()
Linear()
```
or you can construct a dictionary from strings to algos if the list of algos is long
```julia
julia> b = Dict("Linear"=>Linear())
Dict{String,Linear} with 1 entry:
"Linear" => Linear()
julia> b[algo_str]
Linear()
```
But second one has the problem of type-stability if more algos is mixed in dictionary.
---
### Author:  [@tkf](https://discourse.julialang.org/u/tkf)
#### Post date: [May 3, 2019, 8:38am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/6 "2019-05-03T08:38:46Z")
If you don’t want to use a macro, `getproperty(Main, Symbol(algo_str))` does the job.
---
### Author:  [@Eric\_Chen](https://discourse.julialang.org/u/Eric_Chen)
#### Post date: [May 3, 2019, 8:41am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803/7 "2019-05-03T08:41:13Z")
Thank you! problem solved.