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[](https://github.com/egobrain/emodel)
[](https://hex.pm/packages/emodel)
EModel
======
Erlang data transformation/validation library.
Example
===
Map model
---
```erlang
1> Model = [
{<<"login">>, required, string, login, [non_empty]},
{<<"notifyAt">>, required, datetime, notify_at, []},
{<<"type">>, required, {strlist, {enum, [sms, email, twitter, fb]}}, type, [], [email]},
{<<"title">>, required, string, title, [non_empty]},
{<<"message">>, optional, string, msg, []}
].
```
### Success
```erlang
2> Data = #{
<<"login">> => <<"egobrain">>,
<<"notifyAt">> => <<"2088-12-07T8:00:00Z">>,
<<"type">> => <<"email,sms">>,
<<"title">> => <<"Happy 100 birth day!">>,
<<"message">> => <<"Hooray!!!">>
}.
3> emodel:from_map(Data, #{}, Model).
{ok,#{login => <<"egobrain">>,
msg => <<"Hooray!!!">>,
notify_at => {{2088,12,7},{8,0,0}},
title => <<"Happy 100 birth day!">>,
type => [email, sms]}}.
```
### Error
```erlang
3> Data = #{
<<"login">> => <<"">>,
<<"notifyAt">> => <<"2088-12-07T8-00-00Z">>,
<<"type">> => <<"email,sms,vk">>,
<<"msg">> => <<"Hooray!">>
}.
4> emodel:from_map(Data, #{}, Model).
{error,[{<<"login">>,<<"is empty">>},
{<<"notifyAt">>,<<"bad datetime">>},
{<<"type">>,[{3,<<"unknown">>}]},
{<<"title">>,required}]}
```
Tuple model
---
```erlang
1> rr(data, {login, notify_at, type, title, msg}).
2> Model = [
{<<"login">>, required, string, #data.login, [non_empty]},
{<<"notifyAt">>, required, datetime, #data.notify_at, []},
{<<"type">>, required, {strlist, {enum, [sms, email, twitter, fb]}}, #data.type, [], [email]},
{<<"title">>, required, string, #data.title, [non_empty]},
{<<"message">>, optional, string, #data.msg, []}
].
3> emodel:from_map(Data, #data{}, Model).
{ok,#data{login = <<"egobrain">>,
notify_at = {{2088,12,7},{8,0,0}},
type = [email, sms],
title = <<"Happy 100 birth day!">>,msg = <<"Hooray!!!">>}}.
```
Model description
===
Model description is a list of rules which will be applied from top to down.
```erlang
%% M - is a model (tuple or map)
%% A - is a value stored by ext_key() in given data (map or proplist)
%% B - converted data
%% R - error reason
-type rule(M) ::
{name(), required(M), data_converter(A,B,M,R), position(), [validator(B,M,R)], default_value(M,B,R)} |
%% Default may be omitted
{name(), required(M), data_converter(A,B,M,R), position(), [validator(B,M,R)]} |
%% Also for complex cases rule can be
{name(), required(M), setter(A,M,R)}.
-type name() :: any(). %% Key in given map or proplist.
-type position() :: %% Key or position in model
any() | %% for map
non_neg_integer(). %% for tuple
-type required(M) :: req_opt() | fun((M) -> req_opt()).
-type req_opt() ::
optional | %% Value in resulting model is optional
required | %% Value is required
ignore . %% rule will be ignored
-type data_converter(A,B,M,R) :: converter(A,B,M,R) | Type :: term().
-type converter(A,B,M,R) :: fun((A) -> {ok,B} | {error,R}), %% declared in emodel_converters.
:: fun((A,M) -> {ok,B} | {error,R}).
-type data_validator(B,M,R) ::
Type :: term(),
fun((B) -> ok | {error, R}) |
validator(A,B,R).
-type validator(B,M,R) ::
fun((B) -> ok | {error,R}) | %% declared in emodel_validators.
fun((B,M) -> ok | {error,R}).
-type default_value(M,B,R) ::
B :: any() |
fun((M) -> {ok,B} | {error,R}) |
fun((M, Setter) -> {ok, M} | {error, R}) where
Setter :: fun((B,M) -> {ok,M}|{error,R}).
-type setter(A,M,R) -> fun((A,M) -> {ok,M} | {error,R}).
```
All converter or validator ```Type``` params will be converted to
```converter(A,B,R)``` or ```validator(B,M,R)``` at compile call,
using ```converters``` and ```validator``` **options** or
default ```emodel_converters:get_converter/2``` and ```emodel_validators:get_validator/2``` functions.
So you can declare your own simple or complex types and validators.
Types
---
Simple:
- integer
- float
- boolean
- date
- time
- datetime
- string
Complex types are:
- enum (value must exists in given list, ```{enum, [sms, email]}```
- list (example, ```{list, integer}```)
- ulist (unique list, ```{ulist, integer}```)
- strlist (list as string like ```<<"1,2,3,4">>```)
Validators
---
- '>' (numbers validation, usage example ```{'>', 3}```
- '>='
- '<'
- '=<'
- non_empty (check that string is non empty)
- each (check each array item with the given rules, ```{each, [non_empty]}```
Custom converters and validators
===
You can define your custom converter or validator right in code
```erlang
[
{<<"type">>, required, {enum, [daily, monthly]}, type, []},
{<<"month">>,
fun(#{type := monthly}) -> require; %% Custom req fun
(_) -> ignore
end,
fun(<<"Jan">>) -> {ok, 1}; %% Custom converter
(<<"Feb">>) -> {ok, 2};
...
(_) -> {error, <<"Must be valid month short name">>}
end,
m,
[
fun(V) -> %% Custom validator
case V > element(2, erlang:date()) of
true -> ok;
false -> {error, <<"Must be greater than current month">>}
end
end
],
fun(_ModelMap) -> {_,M,_} = erlang:date(), M end %% Lazy default value
}
].
```
or define easily reusable type via options
```erlang
month_short_name(<<"Jan">>) -> {ok, 1};
month_short_name(<<"Feb">>) -> {ok, 2};
...
month_short_name(_) -> {error, <<"Must be valid month short name">>}.
gt_than_cur_month(V, _Model) ->
{_, CurMonth, _} = erlang:date(),
fun(V, _Model) -> %% Custom validator
case V > CurMonth of
true -> ok;
false -> {error, <<"Must be greater than current month">>}
end
end.
get_converter(month, _Opts) -> emodel_converters:get_converter(fun month_short_name/1); %% custom get_converter must return fun/2, emodel_converters:get_converter will automaticly lift your functions
get_converter(Type, Opts) -> emodel_converters:get_converter(Type, Opts).
get_validator('> cur_month', _Opts) -> fun gt_than_cur_month/2;
get_validator(V, Opts) -> emodel_validators:get_validator(V, Opts).
%% In this case it's better to define your own function with default opts
from_map(Data, Model, Description) ->
emodel:from_map(Data, Model, Description, #{
converters => fun get_converter/2,
validators => fun get_validator/2
}).
%% Usage
from_map(Data, #{}, [
{<<"month">>, required, month, m, ['> cur_month']}
]).
```
Compile
===
Model will be compiled automatically each time you use it via ```from_map/_``` or ```from_proplist/_``` functions.
If you want to use model several times, it's event better to compile model first.
For example, when you want to parse list of objects, it's better to write
```erlang
1> CompiledModel = emodel:compile([
{<<"login">>, required, string, login, []},
{<<"password">>, required, string, password, []},
...
], map). %% You must explicitly specify the type of model you want to build
2> emodel:list(Data, fun(ItemData) -> emodel:from_map(ItemData, #{}, CompiledModel) end).
{ok, [#{login => <<"james">>, password => <<"qw67HJ1">>},
#{login => ...
...
]}.
```
Real world example
===
```erlang
%% cowboy 1.0 handler
get_json(Req, State) ->
{QsVals, Req2} = cowboy_req:qs_vals(Req),
Result = emodel:from_proplist(QsVals, #{}, [
{<<"limit">>, optional, integer, limit, [{'>', 0}]},
{<<"offset">>, optional, integer, offset, [{'>=', 0}]},
{<<"fields">>, required, {strlist, {enum, [id,name,isArchived]}}, fields, [], [id, name]}
]),
case Result of
{ok, #{limit := L, offset := O, fields := F}} ->
%% Get data using L,O,F
{error, Reason} ->
%% Encode end set error
end.
```
