What do we know about the classification of "how-not-to-do" techniques or anti-patterns in programming? Usually only the famous Public Morozov comes to mind:
Antipattern Public Morozov. A descendant class created in accordance with this antipattern produces upon request all the data of the ancestor class, regardless of the degree of its hiding. /* a.h */ class A ( private: int papini_dengi; ); /* main.cpp */ #include #define private public /**/ #define protected public /**/ #include "a.h" #undef private /**/ #undef protected /**/ int main() ( A *a = new A(); std::cout papini_dengi; /*And papini_dengi was a private property :) */ system("pause>nul"); return 0; )In fact, there are many more of them. In fact, this magical list from the English-language Wiki already has everything. But I’ll expand the problem a little and show how behavioral-organizational anti-patterns, and more or less “purely software” terms. Below is located alphabetical list some of them, with additions from myself :)
- Abstraction inversion: implemented system functions, needed by users, are not represented, forcing them to re-implement these functions using higher-level functions
- Action at a distance: Unexpected interaction between distant parts of the system.
- Analysis paralysis: Unjustified attention and expenditure of time/resources on the analysis stage
- Big ball of mud, Yo-yo problem, Spaghetti code, Hindu code: The structure of the system is missing or cannot be understood
- Bystander effect: the statement of the problem itself is incorrect, but those who know this are silent, because we still can’t cope with the available forces
- Call super (Call daddy): To implement functionality, a method of a descendant class must necessarily call the same methods of the ancestor class
- Cargo cult programming (cult of the Furry Guru): Using solutions and techniques without understanding the reasons
- Cash cow: The product is profitable and successful, new versions are made through one place and just for show, like Melkosoft
- Circular dependency: A relationship between two or more modules that directly or indirectly depend on each other to proper operation(mutually recursive)
- Coding by exception: Adding new code to support each special recognized error
- Continuous obsolescence (Forever old): we are forced to only adapt the program to new versions of something out there, spending an inordinate amount of time on it
- Copy and paste programming - Copying or slightly modifying existing code instead of creating generic solutions
- Database-as-IPC: Using a database to exchange messages between processes where more lightweight methods can be used
- Death march: Everyone knows that the project is doomed, except the boss, who is the last to know about it. Also usually associated with free overtime work to achieve a obviously impossible result.
- Design by committee: Many have done it, but everyone has their own vision. The result is the absence of even a hint of integrity in the product
- DLL Hell - Problems with shared libraries
- Error hiding: Intercepting an error message before it is shown to the user, resulting in the user not receiving an error message or receiving a meaningless message
- Escalation of commitment: Inability to abandon a decision even when proven wrong
- Feature creep (Futurit): "improvements that lead to excessive complexity of the system at the expense of quality
- Finnish profanity (Finnish swearing): I don’t know why it’s not Russian... I mean aggressive, boorish management style
- God object (Blob): Concentrating too many functions in one class
- Gold plating (Martyshkin’s work): the project has not been profitable for a long time, but work on it continues; main domestic method of work
- Groupthink (Politburo): Nobody wants to put forward ideas that go against a comfortable consensus
- Hard coding: embedding input or configuration data directly into source program or other executable object or fixed formatting of data rather than obtaining that data from external sources
- Inner-platform effect: unjustified complexity of the system, an attempt at excessive versatility
- Input kludge: Lack of correct handling of possible incorrect input. Classic buffer overflow, for example, here
- Knight in shining armor: appears when everything is broken and tries to fix everything without explaining how or why he will do it
- Lava flow: Keeping unwanted (redundant, low-quality) code because removing it is too expensive or would have unpredictable consequences
- Loop-switch sequence: Encoding a sequence of steps using a loop and a select statement
- Magic number: constants in code without explanation of why they are used
- Magic pushbutton: Writing business logic in the user interface code (for example, in a button click event handler)
- Moral hazard (“Effective management”): The one who makes decisions is not responsible for their consequences
- Mushroom management: Managers keep those who work in the dark and feed them manure, in other words, employees do not have enough reliable information to produce anything meaningful
Examples of syntactically correct variable names:
Example of incorrect names:
There is one general rule (for all programming languages) regarding variable naming. The rule is very simple: names should always be meaningful.
Example of poorly readable code
Brevity, of course, is the essence of talent, but sacrificing the ease of perception of code for the sake of its compactness is unwise. Moreover, the length of the name does not affect the performance of the script in any way. But you shouldn’t go to the opposite extreme - giving variables names that are too long. If the name must consist of two or more words, parts of the name must be highlighted in capital letters or separated by underscores. For example, the name $strusernameadndomain is much better understood as $str_UserNameAndDomain.
Example of highly readable code
There are two types of variables: regular variables (value variables) and reference variables. Key Difference between them lies in the way the data is processed. When assigning a value to a regular variable, the assigned value is completely copied, i.e. a new memory block is created where a copy of the original value is placed. During further work, all changes will be reflected on this copy, and not on the original data.
Reference variables work differently. When assigning a value to a reference variable, it is not the data that is copied, but information about where it is located. The result is that the variable points to the same block in which the original data lies. Now if you change the value of the reference variable, the original value will change.
Let's look at an example:
Passing variables by value
There are special functions in PHP for working with variables:
isset() - checks whether a variable has been declared and whether its value is different from NULL;
empty() - analogue of isset()
unset() is a built-in language function that removes the value of a variable and removes the variable itself from the list of available variables (destroying the variable).
$name = "Ivan Ivanovich";
if(isset($name))
{
// Print a message with the name
echo "My name: $name";
// destroy the variable
unset($name);
}
else "Name not yet defined";
echo $name;
// will not output anything,
// because $name variable value
// not yet defined
// or the variable has already been destroyed
Variable Scope
A very important characteristic of a variable is its scope (scope), i.e. a description of where in the program (script) its value can be read or changed. You should always remember that a variable declared inside a program block is visible only within that block, and in order to access a variable declared outside the block, it must be declared in a special way.
The program blocks in this case are “script”, “function” or “class”. For example:
Everything seems to be correct, but it doesn’t work. Why? Because unless you explicitly say that the variable $name inside a function is actually the global variable $name, then the interpreter will create a temporary copy of the variable with the name $name and an empty value. And since the value is empty (undefined), the result of adding strings will be undefined (empty).
Correcting the situation is very easy, just add one line (in bold):
IN in this example the $name variable has a scope equal to the entire script, and a $fullName variable declared inside a function has a scope equal to the function itself. This means that when their function exits, the $fullName variable will be destroyed, and all attempts to read its value will result in an error.
We will look at examples of working with classes in the “Classes and Inheritance” section.
Variable variables
Yes, yes, there is no error here, this is exactly what (in two words) some variables are called in PHP. The idea is that the text part of a variable name (i.e. the name without the dollar sign) can itself be a name. For example:
It is strongly recommended not to use such techniques unless absolutely necessary. Code stuffed with such tricks is very difficult to maintain. This is especially important when working with data entered by users. The main cause of complexity is implicit dependencies. For example, what happens if instead of the name "Vasya" you write something like """""_;%//^q""? That's right! In most cases the script will not be able to execute! You can, of course, add a bunch of checks for the presence "wrong" symbols, but it's easier not to use such tricks at all.
Constants
A constant is a certain unchanging value. A constant is declared with both a name and a value. To declare a constant, use the define() function, and to determine the presence of a constant (i.e., whether it was defined or not) use the defined() function. The name of a constant is constructed according to the same rules as the names of variables.
Examples of constants:
Separate view PHP constants- the so-called "magic constants". These are system constants whose value is determined and set by the interpreter. There are a few such constants:
LINE__ Contains the current line number in the current file.
__FILE__ Contains the full name of the current file
__FUNCTION__ Contains the name of the current function.
__CLASS__ Contains the name of the current class.
__METHOD__ Contains the name of the current method of the current class.
These constants are very convenient for debugging, but in all other cases it is better not to use them, replacing them with calls to the corresponding functions
Hello, Habr!
Today I'd like to introduce newbie webmasters to a variety of neat ways to use output buffering in PHP. Experienced webmasters are unlikely to find anything useful here. Although - who knows?
As you all know, output buffering in php is controlled by a set of functions starting with “ob_”. The most important of them is ob_start. When launched, it collects subsequent output, that is, all kinds of print(), echo, etc., which is then given to the visitor in the form of an html page. And if we started buffering before outputting, then we can finally do something with this almost ready page.
For example, we want to filter out all links to external sites.
Our forum, as old as the ax of Australopithecus, is swarming with a great many spammers, luring visitors to places filled with debauchery, one-armed bandits and political agitation. We could use js with tracking, but we want to change all these links like this instead:
"http://blackjack-hookers.com" => "http://myoldforum.ru/redirect.php?url=blackjack-hookers.com"
The method may not be the most effective, but it is effective. We wrote redirect.php with a filter and a blacklist, and now we need to convert all the links on thousands of forum pages. Using ob_start and a couple regular expressions We'll do it in just a few lines:
Function f_callback($buffer)( $buffer = preg_replace("#http://(www.)?myoldforum\.ru/#","/",$buffer); $buffer = preg_replace("#href="http ://([^"]*)"#","#href="/redirect\.php\?url=$1",$buffer); return $buffer; ) ob_start(f_callback);
Now, by including this code at the beginning of index.php, or another file that the server accesses when viewing pages, we will get what we need.
By changing the content in this way, we are not limited by the engine's methods. This can be very valuable. For example, you can add a plugin:
Function generate_plugin() ( /*generate something*/ ) function f_callback($buffer)( /*...*/ $buffer = str_replace ("",generate_plugin(),$buffer); /*...* / return $buffer; ) ob_start("f_callback");
Now, where we added to the content, what we wanted will appear. One of the applications is inserting a js widget onto a website page. For example, Yandex maps. Usually this is not difficult, but sometimes a poorly written website page editor escapes quotes and curly braces, breaking the widget. As you can see, this problem is easily solved.
The set of PHP tools for working with the output buffer is rich, and is not limited to just ob_start. The methods described above are in some cases overly resource-intensive and cumbersome, since they operate on the entire page. We can process only part of it by creating a wrapper in the template around the generation of something that we don’t want to get into, but that definitely needs to be fixed:
(GENERATE BIG CRAZY THING)
You must have already noticed all these phrases: “I don’t want to get into it,” “as ancient as a tyrannosaurus chair,” “a crookedly written editor”... In an ideal world, shells around the output buffer are not needed. Everything that can be done with ob_start could theoretically be done without it. This technique sometimes introduces confusion into the project code; many see its meaning only in sending the output to ob_gzhandler for compression, and consider its use in other cases dangerous. But often you simply cannot do without output control.
Especially if you don’t want to dig deep.
jQuery Effects Definition and ApplicationThe jQuery .show() method allows you to show hidden selected elements. To hide selected elements you can use the .hide() method.
Please note that when the .show() method is used without parameters, the element is displayed without animation. This is equivalent * to using the .css() method with the following value:
$(selector).css("display ", "block ")
* - except that the value of the display property is stored internally by jQuery and can later be restored to its original value.
If you use element styles with !important , then the .show() method will not be able to display the element. In this case, it is recommended to use methods such as .addClass() , .removeClass() , .toggleClass() , or .attr() .
jQuery syntax: Syntax 1.0: $(selector).show() // method used without parameters $(selector).show( duration, complete) duration- Number , or String complete- Function $(selector).show(( options) ) // option: value (description below) options- PlainObject Syntax 1.4.3: $(selector).show( duration, easing, complete) duration- Number , or String easing- String complete- Function Added in jQuery 1.0 (syntax updated in version 1.4) Parameter values| duration | A string or numeric value that specifies how long the animation will last. The default value is 400 (in milliseconds). The string keywords "fast" and "slow" correspond to 200 and 600 milliseconds respectively (high values indicate slow animation, lower values indicate fast animation). |
| easing | Keyword (string) that defines the speed curve for the animation (used mathematical function- cubic Bezier curve). Without using external plugins has only two meanings - linear(animation effect with the same speed from start to finish) and swing(the animation effect has a slow start and a slow end, but the speed increases in the middle of the animation). Default value swing. |
| complete | A function that will be executed after the animation has completed, it is called once for each matching element. Inside the function, the this variable refers to the DOM element to which the animation is applied. |
| options |
|
$("p").show(); // display all elements
) ); ) ); Hide Show
First paragraph
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.hide() and .show()
in the document.
The result of our example:
.hide() and .show() are different animation durations:
Using jQuery methods .hide() and .show() (different animation speeds) $(document).ready(function ()( $(".hide ").click(function ()( // set the function when the element is clicked with class hide $("p:first ").hide("slow "); // hide the first elementIn the document $("p:nth-of-type(2) ").hide(2000 ); // hide the second element
In the document $("p:last ").hide("fast "); // hide last element
In the document ) ); $(".show ").click(function ()( // set the function when clicking on an element with class show $("p:first ").show("slow "); // display the first element
In the document $("p:nth-of-type(2) ").show(2000 ); // display the second element
In the document $("p:last ").show("fast "); // display the last element
In the document ) ); ) ); Hide Show
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In this example, using the jQuery .hide() and .show() methods, when a certain button is clicked, we hide or show all elements
in the document. Wherein first element
hidden or displayed behind 600 milliseconds ( keyword "slow"), second element for 2000 milliseconds, and third behind 200 milliseconds (keyword "fast").
The result of our example:
Consider the following example in which we set the .hide() and .show() methods not only for the duration of the animation, but also for the animation speed and the function that will be executed after the animation is completed:
Using jQuery methods .hide() and .show() (with callback function) $(document).ready(function ()( $(".hide ").click(function ()( // set the function when the element is clicked with class hide $("p ").hide(500 , "linear ", function ()( // hide elementsIn the document $(".status ").text("Elements have disappeared "); // set a function when clicking on an element with class show $("p ").show(500 , "linear ", function ()( // display elements
In the document $(".status ").text("Elements appeared "); // add text information to the element with class status ) ); ) ); ) ); Hide Show
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Third paragraph
In this example, using the jQuery .hide() and .show() methods, when a certain button is clicked, we hide or show all elements
in the document. At the same time, we specified for our methods an animation duration equal to half a second (500 milliseconds), the animation effect occurs at the same speed from start to finish ( linear) and a function that, after the animation is complete, finds an element with the class status and adds text information(jQuery .text() method).
The result of our example:
Consider the following example in which we pass as a parameter to the .hide() and .show() methods an object containing various options that will control the animation:
Using jQuery methods .hide() and .show() (options object as parameter) $(document).ready(function ()( $(".hide ").click(function ()( // set the function when clicking on an element with the hide class $("p ").hide(( // hide elementsIn the document duration: 800 , easing: "linear ", // animation speed The elements have disappeared "); ) , queue: false // do not queue ) ) ) ); $(".show ").click(function ( )( // set a function when clicking on an element with class show $("p ").show(( // display elements
In the document duration: 800 , // animation duration easing: "linear ", // animation speed complete: function ()( // callback $(".status ").text("Elements have appeared "); ) , queue: false // don't put in queue ) ); ) ); ) ); Hide Show
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In this example, using the jQuery .hide() and .show() methods, when a certain button is clicked, we hide or show all elements
in the document. In this case, we pass an object containing the following parameters as method parameters:
- animation duration equal to 800 milliseconds ( duration: 800)
- the animation effect occurs at the same speed from start to finish ( easing: linear)
- a function that, after the animation completes, finds an element with a class status and adds text information ( complete: function).
- animation is not placed in the effects queue ( queue: false).
The result of our example.
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