In the following example, how can I redefine one property of the predefined block style in the tikzpicture environment without affecting the others:
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.12}
\tikzstyle{block} = [rectangle, draw,minimum width=3em,]
\begin{document}
\begin{tikzpicture} % This works ok
\node[block, minimum width=3em,] (b1) {B1};
\end{tikzpicture}
\begin{tikzpicture}[block/.style={minimum width=3em,}] % This reset all styles
\node[block] (b1) {B1};
\end{tikzpicture}
\end{document}


tikz/pgfplotsshould be awarded the Most Confusing Syntax Award. – jak123 Jun 10 '15 at 08:00pstricks. – Henri Menke Jun 10 '15 at 09:49