[FieldArray] Pass reference to the fields prop in map, forEach, and reduce callbacks

[Whoaa512]

It's probably not well know but creating functions inline within a render call is a performance hit since new functions are created on each re-render. This in turns clutters our memory space and makes the GC work unnecessarily.

To avoid this it would be helpful if fields.map, fields.forEach, and fields.reduce passed along a fields reference to the callback provided. This allows us to create a callback method that can be passed directly the fields.map while still allowing access to swap, remove, pop, etc.

Example:

 const renderSubFields = (member, index, fields) => (
     <li key={index}>
       <button
         type="button"
         title="Remove Member"
         onClick={() => fields.remove(index)}/>
       <h4>Member #{index + 1}</h4>
       <Field
         name={`${member}.firstName`}
         type="text"
         component={renderField}
         label="First Name"/>
       <Field
         name={`${member}.lastName`}
         type="text"
         component={renderField}
         label="Last Name"/>
     </li>
 )
 const renderMembers = ({ fields }) => (
   <ul>
     <button type="button" onClick={() => fields.push({})}>Add Member</button>
     {fields.map(renderSubFields)}
   </ul>
 )

[codecov-io]

Current coverage is 100% (diff: 100%)

Merging #2187 into master will not change coverage

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[erikras]

Nicely done!

[erikras]

Published in v6.2.1.

[lock]

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