Q: TikZ: Arrow hidden by circle around node Context
I would like to draw lines between nodes to indicate a dependence relationship. The nodes are drawn as circles. Unfortunately the arrow is hidden by the circle.
Question
How can I shorten the line such that there is a gap between the line and both circles?
Code
\draw [color=black, fill=black] (1.00, 0.00) circle (.1);
\draw [color=black, fill=black] (2.00, 0.00) circle (.1);
\draw (1.00, 1.00);
\draw (2.00, 1.00);
\draw [color=white] (2.25, 1.25) circle (.1);
\path [draw, ->] (1.00, 0.00) -- (2.00, 0.00);
\path [draw, ->] (1.00, 1.00) -- (2.00, 1.00);

Output:


A: Options shorten > and shorten < can be used to shorten a line or arrow.
The following example shortens the arrow at both ends by the radius of the circles and some extra space, e.g. the line width:
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\draw [color=black, fill=black, radius=.1]
  (1, 0) circle[]
  (2, 0) circle[]
;
\draw [
  ->,
  shorten <=.1cm + \pgflinewidth,
  shorten >=.1cm + \pgflinewidth,
] (1, 0) -- (2, 0);
\draw [->] (1, 1) -- (2, 1);
\end{tikzpicture}
\end{document}





A: While it was being suggested to you in the comments, I was slightly modifying your code to show you that you should have used nodes. The arrow properties can also be set globally in the \tikzpicture options without having to type it in each arrow, by using the Tikz library arrows.meta. 
I also think that if you need to draw arrows, you're better off saying \draw ... than \path[draw] ..., which is very useful for drawing invisible paths for calculating coordinates.
Lastly, I'm not sure what the commands in the middle were supposed to do:
\draw (1.00, 1.00);
\draw (2.00, 1.00);
\draw [color=white] (2.25, 1.25) circle (.1);

Except for the circle (not at either side of the arrows), the other commands didn't do anything (if I missed their purpose, let me know).

\documentclass[margin=10pt]{standalone}
\usepackage{tikz}

\usetikzlibrary{arrows.meta}

\begin{document}
\begin{tikzpicture}[->] % add ,>=latex or ,>=stealth to change arrow tip

\node [circle, draw, fill=black] (a1) at (1,0) {};
\node [circle, draw, fill=black] (a2) at (2,0) {};

\node [circle, draw, fill=white] (b1) at (1,1) {};
\node [circle, draw, fill=white] (b2) at (2,1) {};

\draw (a1) -- (a2);
\draw (b1) -- (b2);

\end{tikzpicture}
\end{document}

