ch09.htm

delphi自学的好教材！特别适合刚刚起步学习delphi的人员！同样对使用者具有参考价值！

	
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<P>You can also open multiple files at one time. To open multiple files, choose the
files you want to open in the Open dialog box and click OK. Each file selected will
be loaded, and a tab for each file will be placed at the top of the editor window.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> You can also use drag-and-drop to open files. For example, you can
	choose a file (or a group of files) in Explorer, drag it onto the Code Editor, and
	drop it. The file will be opened in the Code Editor. 
<HR>


</BLOCKQUOTE>

<P>To save a file, choose File|Save or File|Save As from the main menu or type Ctrl+S
on the keyboard. If the file has not been previously saved, the Save As dialog box
will appear, and you can enter a filename at that time.</P>
<P>
<H3><A NAME="Heading17"></A>Highlighting Text</H3>
<P>Although text highlighting is basic text-editor stuff, I thought it wouldn't hurt
to remind you of a few basic highlighting techniques you can use in the Delphi Code
Editor.</P>
<P>To highlight a short block of text, you can use the mouse to drag across any text
you want to highlight. After you've selected the text, you can cut, copy, or paste
as needed. To highlight longer blocks of code, you can use the Click+Shift+Click
method. First, click at the beginning of the block you want to highlight. Next, hold
the Shift key on the keyboard and then click again at the end of the block. All text
between the starting point and the ending point is highlighted.</P>
<P>Another useful feature is the capability to quickly select an individual word.
To select a keyword, function name, or variable, just double-click on the word. Now
you can perform any editing operations you want with the highlighted word.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> To select a single line of code with the mouse, click at the beginning
	of the line and drag straight down to the beginning of the next line. To highlight
	a single line of code with the keyboard, first press the Home key to move to the
	beginning of the line and then use Shift+down-arrow key to highlight the line. 
<HR>


</BLOCKQUOTE>

<P>Dozens of keyboard combinations can be used to highlight text and do other editing
chores. For a complete list of all the keyboard shortcuts available, consult the
Delphi online help.</P>


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	<P>
<HR>
<strong>TIP:</strong> As you program you often add, delete, or move blocks of text. Sometimes
	you will need to indent an entire block of code. At other times you will need to
	un-indent (outdent?) an entire block of code. To indent a block of code, highlight
	the lines that you want to indent and then press Ctrl+Shift+I on the keyboard. The
	entire block will be indented. To un-indent a block of code, press Ctrl+Shift+U on
	the keyboard. 
<HR>


</BLOCKQUOTE>

<P>The Code Editor also supports drag-and-drop editing. To move a section of code,
first highlight it. Next, place the mouse cursor over the highlighted text and drag.
Drag until the cursor reaches the location where you want the code to be placed.
Release the mouse button and the code will be moved to the new location. To copy
text rather than move it, repeat the preceding steps but hold down the Ctrl key before
you drop the text.</P>
<P>
<H4>Undo</H4>
<P>The Code Editor has a virtually limitless number of undo levels (32,767 by default).
Normally, you can only undo commands up to the last time you saved a file. By changing
the editor options, you will be able to undo past commands even after saving the
file. I'll talk about editor options and preferences later in the chapter in the
section titled &quot;Changing the Editor Options.&quot;</P>
<P>In general, it pays to remember this simple maxim: &quot;Undo is your friend.&quot;</P>
<P>
<H4>Find and Replace</H4>
<P>Find and Replace are used fairly heavily in programming. You might use Find to
find a specific piece of code or a specific variable in your code. You might use
Replace to change a variable's name or to change the name of a method. The possibilities
are endless.</P>
<P>The Delphi Find Text and Replace Text dialog boxes implement more or less standard
find-and-replace operations. To bring up the Find Text dialog box, choose Search|Find
from the main menu or press Ctrl+F. Enter text in the Text to find field and click
OK or press Enter. If the text is found, it will be highlighted.</P>


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<strong>NOTE:</strong> Text highlighted by the Find Text dialog box is not the same as text
	highlighted with the mouse. You will notice that searched text is highlighted in
	black whereas text selected with the mouse is highlighted in blue (assuming you haven't
	changed the editor defaults). Text highlighted after a search operation is not selected
	for editing, it's just marked so that you can see it better. 
<HR>


</BLOCKQUOTE>

<P>To invoke the Replace Text dialog box, choose Search|Replace from the menu or
press Ctrl+R. Figure 9.12 shows the Delphi Replace Text dialog box. With a few obvious
exceptions, the Find Text dialog box contains the same options.</P>
<P>For the most part, the options on the Find Text and Replace Text dialog boxes
do exactly what they indicate. If you choose the Case Sensitive option, you must
type the search text exactly as it appears in the source file.</P>
<P><A HREF="javascript:popUp('28670912.gif')"><B>FIGURE 9.12.</B></A><B> </B><I>The
Replace Text dialog box.</I></P>

<P>Use the Whole Words Only option when you want to be sure that text for which you
are searching is not part of a longer word or variable name. For example, let's say
you want to replace Form with MyForm. In this case, you would want to search for
whole words only because the word Form might be used in other variable names (such
as TForm).</P>
<P>The Regular Expressions option requires explanation as well. When this option
is on, you can use special and wildcard characters when doing searches. The special
characters enable you to find elements such as the beginning of a line or the end
of a line in your search strings. Wildcard characters work much like they do in directory
operations. For a complete description of regular expressions, see the Delphi online
help under the topic &quot;Regular Expressions.&quot;</P>
<P>When replacing text, it is safest to leave the Prompt on Replace option on. When
you do a Replace All operation with this option on, the editor will highlight each
found word and prompt you whether to replace it. It is easy to miscalculate the results
of a Replace All operation, so always use Replace All with care. Even then, it still
pays to remember that maxim: &quot;Undo is your friend.&quot;</P>
<P>The rest of the Find and Replace options are self-explanatory and therefore don't
need additional mention.</P>
<P>
<H4>Find in Files</H4>
<P>Find in Files is a great tool for searching for text in multiple files. I frequently
use Find in Files to search the VCL source code for particular methods, variables,
or classes. This tool is useful and convenient, and you should learn how to use it.</P>
<P>To display the Find Text dialog box, you can choose Search|Find in Files from
the main menu. Perhaps an easier way is to type Ctrl+F on the keyboard to bring up
the Find Text dialog box and then click the Find in Files tab. Figure 9.13 shows
the Find Text dialog box with the Find in Files tab showing.</P>
<P><A HREF="javascript:popUp('28670913.gif')"><B>FIGURE 9.13.</B></A><B> </B><I>The
Find Text dialog box.</I></P>

<P>Find in Files uses some of the same search options as the regular Find operation
(case-sensitive, whole word only, and regular expressions). In addition, you have
the option to search all files in the project, all open files, or files in a particular
directory, including subdirectories.</P>
<P>When you start Find in Files, a small window with a title of Searching appears
in the lower-right portion of your screen. This window shows the status of the Find
in Files operation. It will show you the current file being searched and the number
of matches up to this point. To cancel the search, just close the Searching window.</P>
<P>Any matches are reported in the Code Editor's message window. The message window
shows the filename of the file in which the text was found, the line number where
the text was found, and the line containing the search text with the search text
displayed in bold. To view the file that contains a match, just double-click a line
in the message window. Delphi will open the appropriate file and display the exact
line containing the text for which you are searching. Figure 9.14 shows Delphi searching
a set of files.</P>
<P>When specifying the file mask, all the usual wildcard characters apply. For example,
if you want to search all text files in a directory, you would enter the following
in the File masks field:</P>
<P>
<PRE>c:\MyStuff\*.txt
</PRE>
<P>Find in Files is an indispensable tool. I find myself using it all the time. Learning
to use Find in Files will save you a lot of time.</P>
<P><A HREF="javascript:popUp('28670914.gif')"><B>FIGURE 9.14.</B></A><B> </B><I>Delphi
searching for text.</I>
<H4>Getting Help</H4>
<P>One of the most useful features of the Code Editor is its integration with the
Delphi help system. Just place the editor cursor over an Object Pascal keyword, a
VCL property or method, or any other Delphi-specific text and press F1. If a help
topic for the text under the cursor exists in the Delphi help files, Windows Help
will run with the appropriate page showing. If no help topic exists for the selected
text, an error message will be displayed.</P>
<P>This feature is extremely useful when you can't remember how to use a particular
aspect of Delphi, Object Pascal, or VCL. Help, as they say, is just a keystroke away.</P>
<P>
<H3><A NAME="Heading18"></A>Specialized Editor Features</H3>
<P>The Delphi Code Editor has a few features that are extremely useful when you are
writing a lot of code. They are explained in the following sections.</P>
<P>
<H4>Code Templates</H4>
<P>Code templates are another nice feature of the Delphi Code Editor. Code templates
enable you to insert any predefined code (or any text, for that matter) in your source
units. To use code templates, just type Ctrl+J on the keyboard while editing in the
Code Editor. When you do, a list box will pop up giving you a list of templates from
which to choose. Choose a template from the list, press Enter, and the text corresponding
to that code template will be inserted into your source code. Figure 9.15 shows the
code template list box as it appears when you type Ctrl+J.</P>
<P><A HREF="javascript:popUp('28670915.gif')"><B>FIGURE 9.15.</B></A><B> </B><I>The
Delphi code template list box.</I></P>

<P>You can add new templates or edit existing templates via the Code Insight page
of the Environment Options dialog box. Or, if you prefer, you can open the code template
file with any text editor (such as the Delphi Code Editor) and edit the code templates
there. The code template file is called DELPHI32.DCI and is located in the Delphi
4\Bin directory.</P>
<P>Feel free to modify the code templates in any way you see fit. For example, I
have modified my code template representing the for statement to look like this:</P>
<P>
<PRE>for I := 0 to Pred(|) do begin
end;
</PRE>
<P>Notice the pipe character (|) in the code snippet. The pipe in a code template
entry is a placeholder that determines where the cursor will be placed after the
text is inserted into your source code.</P>


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<strong>TIP:</strong> If you make a lot of modifications to the code template file, be sure
	to keep a backup of the file in a safe location. You will need a backup because the
	Delphi installation program will overwrite your modified DELPHI32.DCI file when you
	update or reinstall Delphi. 
<HR>


</BLOCKQUOTE>

<P>You can use code templates for more than just code. Here at TurboPower Software
our source files always have a header at the top of the unit. It looks something
like this:</P>
<P>
<PRE>{*********************************************************};
{*                 Filename and version                  *};
{*        Copyright (c) TurboPower Software 1998         *};
{*                 All rights reserved.                  *};
{*********************************************************};
</PRE>
<P>Because most of this text stays constant, I have a template that quickly inserts
the header in any new source units I create. Use code templates for any text that
you use frequently in your day-to-day programming.</P>
<P>
<H4>Code Parameters</H4>
<P>The code parameters feature of the Code Editor displays a tooltip that prompts
you with the needed parameters of a VCL method or Windows API function. With hundreds
of VCL methods and Windows API functions, there is virtually no way to remember every
function's parameters. The code parameters feature saves you time by showing you
the parameters of a method as you type. For example, let's say you are calling the
SetBounds method. When you type the opening parentheses, a hint window pops up as
shown in Figure 9.16.</P>
<P><A HREF="javascript:popUp('28670916.gif')"><B>FIGURE 9.16.</B></A><B> </B><I>Code
parameters in action.</I></P>

<P>As you can see in Figure 9.16, each parameter is listed in the tooltip. The parameter
you need to type next is displayed in bold. As you type a parameter, the next parameter
is displayed in bold. This continues until you type all the method's parameters.
After you have typed all the required parameters, the code parameters tooltip disappears.
The code parameters options are set on the Code Insight page of the Environment Options
dialog boxes. I'll discuss that page later in the section &quot;The Code Insight
Page.&quot;</P>
<P>
<H4>Code Completion</H4>
<P>Code completion is another Code Editor feature that can save you development time.
Type a class variable name followed by the dot operator, and the Code Editor will
display a list box with all of that class's properties and methods. If, for example,
you have a memo component called Memo, you will type</P>
<P>
<PRE>Memo.
</PRE>
<P>and pause for a moment. A list box pops up as shown in Figure 9.17.</P>

<P><A HREF="javascript:popUp('28670917.gif')"><B>FIGURE 9.17.</B></A><B> </B> <I>Code
completion displaying the properties and methods of TMemo.</I></P>

<P>When you see the list box, you ca