Jtdcftul

I want to achieve the following:

But the connecting of nodes isn't working properly. I get the following output:

How do I fix this and where am I going wrong.

MWE:

documentclass[tikz]{article}

usepackage{tikz}

tikzset{square/.style = {

    shape  = rectangle,

    fill   = gray!50,

    draw   = black,

    thick

}}



tikzset{circle/.style = {

    shape  = circle,

    fill   = blue!20,

    draw   = blue,

    thick

}}



begin{document}

begin{tikzpicture}

  draw[square] (-4,4)rectangle node (r1) {r1} (-3,5);

  draw[circle] (-1,4.5) circle [radius=0.5cm] node (s1) {s1};

  draw[->] (r1.west) -- (s1.east);



end{tikzpicture}

end{document} 

Please note that I would like to stick to the approach of draw[->] (r1.west) -- (s1.east);

Correct picture

documentclass[tikz,margin=3mm]{standalone}

tikzset{squarenode/.style = {

    shape  = rectangle,

    fill   = gray!50,

    draw   = black,

    thick,

    minimum size=1cm %%%% Take note of this!

},

    circlenode/.style = {

    shape  = circle,

    fill   = blue!20,

    draw   = blue,

    thick,

    minimum size=1cm %%%% and this!

}}



begin{document}

begin{tikzpicture}

  draw (-4,4.5) node[squarenode] (r1) {r1}; % Or node[squarenode] (r1) at (-4,4.5) {r1};

  draw (-1,4.5) node[circlenode] (s1) {s1}; % Or node[circlenode] (s1) at (-1,4.5) {s1};

  draw[->] (r1) -- (s1); % or (r1.east)--(s1.west);



end{tikzpicture}

end{document} 

Some notes (important!)

1. 
   circle is a defined option, therefore you must not define a new circle. I changed it to circlenode.


2. You don't have to draw the circle and the square manually. You can use the shape in the node and minimum size. For more controlling, we have minimum height and minimum width.


3. I don't recommend using many tikzset{}s.


4. 
   tikz is not an option of article. It is an option of standalone. When you load tikz option already, you don't need usepackage{tikz}.

Difference when you use (r1)--(s1) and (r1.east)--(s1.west)

documentclass[tikz,margin=3mm]{standalone}

begin{document}

begin{tikzpicture}

node[draw] (a) at (0,0) {Some text};

node[draw] (b) at (5,3) {Hello world};

draw[thick] (0,0)--(5,3);

draw[red] (a)--(b);

draw[blue] (a.east)--(b.west);

end{tikzpicture}

end{document}

Look closely at the beginning point and the ending point of the red line and the blue line.