Is possible to discontinue chain of nodes?

Question

For example, the image:

can be drawn with following MWE:

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{chains, positioning}

\begin{document}
    \begin{tikzpicture}[
    node distance = 7mm and 7mm,
    start chain = going right,
base/.style = {draw, minimum size=7mm},
 box/.style = {base, on chain, join=by ->}
                        ]
\coordinate (a) at (0,-1);
\node (n1)  [box]   at (0,0) {A};
\node (n2)  [box]   {B};
\node (n3)  [box]   {C};
\node (n4)  [base]   at (a -| n2) {D};
\draw[red,->]   (n3) |- (n4);
\draw[red,->]   (n4) -| (n1);
    \end{tikzpicture}
\end{document}

Now, for some reason I like to have only one definition for nodes and draw above image again:

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{chains, positioning}

\begin{document}  
    \begin{tikzpicture}[
    node distance = 7mm and 7mm,
    start chain = going right,
box/.style = {draw, minimum size=7mm,
              on chain, join=by ->}
                        ]
\coordinate (a) at (0,-1);
\node (n1)  [box]   at (0,0) {A};
\node (n2)  [box]   {B};
\node (n3)  [box]   {C};
\node (n4)  [box]   at (a -| n2) {D};
\draw[red,->]   (n3) |- (n4);
\draw[red,->]   (n4) -| (n1);
    \end{tikzpicture}
\end{document}

Result is expected wrong:

Question: is it possible to say, that node "D" in above MWE is not on the chain? For example as

\node (n4)  [box, suppress chain]   at (a -| n2) {D};

similarly as it can be discontinued join between nodes in chain with definition of new option:

\tikzset{suppress join/.code={\def\tikz@after@path{}}}

and used as

\node (n4)  [box, suppress join]   at (a -| n2) {D};

I looked in TikZ documentation, where is described chainin (page 5449), but didn't find anything with opposite action.

@Dr.ManuelKuehner I think he want to get the first picture with code similar to the second (without base/.style definition) — koleygr, Jul 13 '17 at 23:57

cfr · Accepted Answer · 2017-07-14T00:15:29.383

Something like this?

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{chains, positioning}
\begin{document}
\makeatletter
\tikzset{
  suppress join/.code={\def\tikz@after@path{}},
  off chain/.code={\def\tikz@lib@on@chain{}}%
}
\makeatother
\begin{tikzpicture}[
  node distance = 7mm and 7mm,
  start chain = main going right,
  box/.style = {draw, minimum size=7mm, on chain, join=by ->}
  ]
  \coordinate (a) at (0,-1);
  \node (n1)  [box]   at (0,0) {A};
  \node (n2)  [box]   {B};
  \node (n3)  [box]   {C};
  \node (n4)  [suppress join, off chain, box]   at (a -| n2) {D};
  \draw[red,->]   (n3) |- (n4);
  \draw[red,->]   (n4) -| (n1);
\end{tikzpicture}
\end{document}

Note that the order matters here: off chain must be before box. You can then continue the chain, should you so desire.

\begin{tikzpicture}[
  node distance = 7mm and 7mm,
  start chain = main going right,
  box/.style = {draw, minimum size=7mm, on chain, join=by ->}
  ]
  \coordinate (a) at (0,-1);
  \node (n1)  [box]   at (0,0) {A};
  \node (n2)  [box]   {B};
  \node (n3)  [box]   {C};
  \node (n4)  [suppress join, off chain, box]   at (a -| n2) {D};
  \node [box] {E};
  \draw[red,->]   (n3) |- (n4);
  \draw[red,->]   (n4) -| (n1);
\end{tikzpicture}

Note, however, that the chains library is considered deprecated.

Dear @cfr, yes. I looking for something like this. Thank you very much! By the way, the off chain is sufficient. If the node is not in chain anymore, then macrojoin is not active in this node, so the suppress join is superfluous in this case :) — Zarko, Jul 14 '17 at 00:13

Is possible to discontinue chain of nodes?

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