为什么这段代码绘制的节点周围没有边框？

Question

我正在尝试绘制一个简单的 ER 图。但是，以下代码不会在节点周围产生边框：

\documentclass[tikz]{standalone}

\usetikzlibrary{arrows, calc, positioning, shapes.geometric}

\begin{document}
  \ttfamily
  \begin{tikzpicture}[draw=black, thick, ->, >=stealth,
    entity/.style={ellipse, text centered}
    field/.style={rectangle, text centered}
    relation/.style={diamond, text centered}
    ]

    \node (pilot) [entity] {Pilot};

  \end{tikzpicture}
\end{document}

添加draw=black样式没有帮助。只能通过指定draw节点选项本身，例如

\node (pilot) [draw] {Pilot};

有效。这是为什么呢？

Answer 1

节点不会自动继承全局选项中输入的每个键。手册（第 128 页左右）说，提供全局选项的正确方法是使用键every...。例如，在选项中使用

every node/.style={draw=black, thick},

会做你想做的事。

\documentclass[tikz]{standalone}

\usetikzlibrary{arrows, calc, positioning, shapes.geometric}

\begin{document}
  \ttfamily
  \begin{tikzpicture}[draw=black, thick, ->, >=stealth, red,
    every node/.style={draw=black, thick},
    entity/.style={ellipse, text centered}
    field/.style={rectangle, text centered}
    relation/.style={diamond, text centered}
    ]
    \node (pilot) [entity] {Pilot};
  \end{tikzpicture}
\end{document}