Avoid Local Variables, Use Const

In your +new method:

• Prefer inlining what would otherwise be a single-use temporary local variable.
• If inlining isn't possible due to necessary references or code duplication concerns, add const to the right place to make sure the temporary local variable isn't assignable by (E.g. NSString *const foo instead of NSString *foo).

We avoid reassigning variables because:

• It makes code harder to read and modify since dependencies between local variables are hard to visualize.
• It encourages mutating local variables after assignment which hides surprising side-effects and changes.

Here is a really tangled-up +new method that is hard to read, understand, or modify:

+ (instancetype)newWithArticle:(ArticleModel *)article options:(ArticleOptions)options
  {
    NSAttributedString *timestamp = [CKDateFormatter stringFromDate:article.creationTime];
    HeaderComponent *header =
    [HeaderComponent
     newWithTitle:article.title
     subtitle:timestamp];
    // LOGIC ERROR! timestamp has already been used by header, but no one warns us.
    if (options & ArticleOptionHideTimestamp) {
      timestamp = nil;
    }
    MessageOptions messageOptions = 0;
    if (options & ArticleOptionShortMessage) {
      messageOptions |= MessageOptionShort;
    }
    MessageComponent *message =
    [MessageComponent
     newWithArticle:article
     options:messageOptions];
    FooterComponent *footer = [FooterComponent newWithArticle:article];
    // SUBOPTIMAL: why did we create the header only to throw it away?
    // Also, notice how far this is from where we created the header.
    if (options & ArticleOptionOmitHeader) {
      header = nil;
    }
    return [self newWithComponent:
            [CKFlexboxComponent
             newWithView:{}
             size:{}
             style:{}
             children{
               header,
               message,
               footer
             }]];
  }

Instead, split out logic into separate components:

+ (instancetype)newWithArticle:(ArticleModel *)article options:(ArticleOptions)options
{
  // Note how there are NO local variables here at all.
  return [self newWithComponent:
          [CKFlexboxComponent
           newWithView:{}
           size:{}
           style:{}
           children:{
             [ArticleHeaderComponent
              newWithArticle:article
              options:headerOptions(options)],
             [ArticleMessageComponent
              newWithArticle:article
              options:messageOptions(options)],
             [FooterComponent newWithArticle:article]
           }]];
}
// Note how this is a pure function mapping from one options bitmask to another.
static ArticleHeaderComponentOptions headerOptions(ArticleOptions options)
{
  ArticleHeaderComponentOptions options;
  if (options & ArticleOptionOmitHeader) {
    options |= ArticleHeaderComponentOptionOmit;
  }
  if (options & ArticleOptionHideTimestamp) {
    options |= ArticleHeaderComponentOptionHideTimestamp;
  }
  return options;
}