# `Filtrex.Utils.Encoder`
[🔗](https://github.com/rcdilorenzo/filtrex/blob/main/lib/filtrex/utils/encoder.ex#L1)

Helper methods for implementing the `Filtrex.Encoder` protocol.

# `encoder`
*macro* 

This macro allows a simple creation of encoders using a simple DSL.

Example:
```
encoder "equals", "does not equal", "column = ?", &(&1)
```

In this example, a comparator and its reverse are passed in followed
by an expression where "column" is substituted for the actual column
name from the struct. The final argument is a function (which is not
necessary in this case since it is the default value) that takes the
raw value being passed in and returns the transformed value to be
injected as a value into the fragment expression.

# `intersperse_column_refs`

Intersperses proper Ecto column references between values to be 
queried.

## Examples

    intersperse_column_refs(["post"], "title")
    # => [s.title, "post"]
    
    intersperse_column_refs(["best", "post"], "title")
    # => [s.title, "best", s.title, "post"]

## Background

Ecto queries support string query fragments, but fields referenced in
these fragments need to specifically reference fields, or you will get 
"Ambiguous column" errors for some queries.

In other words:

    # Good
    where(query, [s], fragment("lower(?) = lower(?)", s.title, "post")

    # Bad
    where(query, [s], fragment("lower(title) = lower(?)", "post"))

Interpolating `s.title` into the fragment arguments ensures that joined
tables which also have the `title` column will not conflict.

See `Ecto.Query.API.fragment/1` for more details.

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*Consult [api-reference.md](api-reference.md) for complete listing*