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Understanding Inheritance

From: Dreamweaver CS3 Beyond the Basics

Video: Understanding Inheritance

A previous movie focused on the cascade, another core concept of CSS when determining rendering is the order of inheritance. Order of inheritance is one of the easiest CSS concepts to understand. Essentially it says that any nested tags of a parent tag will inherit the styles of the parent tag. Now not all properties inherit. Margins for example don't inherit. If you placed a 10 pixel margin on the Body tag you wouldn't want every element inside the Body tag to also have that 10 pixel margin. So we have to understand which properties inherit and which don't. There is no big rule on that, as you will just find out through experience. Now the other thing about inheritance is that if you write a style for a child tag, it will overwrite its parent's rendering if there is a conflict and you can see the example of this right on the screen. We have a div with the ID of content surrounding a paragraph that says I am feeling blue and blue is an Em tag. Well, with the rules, the content id is declaring that everything inside of it should be Arial and then the paragraph says, well, yeah but the font size should be 1 em and the color should be red.

Understanding Inheritance

A previous movie focused on the cascade, another core concept of CSS when determining rendering is the order of inheritance. Order of inheritance is one of the easiest CSS concepts to understand. Essentially it says that any nested tags of a parent tag will inherit the styles of the parent tag. Now not all properties inherit. Margins for example don't inherit. If you placed a 10 pixel margin on the Body tag you wouldn't want every element inside the Body tag to also have that 10 pixel margin. So we have to understand which properties inherit and which don't. There is no big rule on that, as you will just find out through experience. Now the other thing about inheritance is that if you write a style for a child tag, it will overwrite its parent's rendering if there is a conflict and you can see the example of this right on the screen. We have a div with the ID of content surrounding a paragraph that says I am feeling blue and blue is an Em tag. Well, with the rules, the content id is declaring that everything inside of it should be Arial and then the paragraph says, well, yeah but the font size should be 1 em and the color should be red.

But the Em tag says no color should be blue and font style should be Normal. Now what's happening here is that the em tag is inheriting its font family and its size from the content in the Paragraph tag. It's overwriting the Paragraph tag as far as color goes and then it's overwriting the browser's default styles to say no don't display me as italicized text, display me as normal. So that's inheritance, it's fairly easy to understand, but as your pages get more complex it can be harder to remember exactly who is the parent style versus the child style. So again paying attention to it and staying focused, make sure that your rendering is going to turn out the way you want. So back in Dreamweaver we are going to return to our Rendering that HTM file we have been working on and we are going to take a look at working with inheritance. So right now we do have some inheritance going on. You will notice the paragraphs, for example, when I click on them, I am getting from the Body tag. I am getting the font family. So the reason that my paragraphs are displaying in this Arial is because they are inheriting that from a parent tag. Well, we are going to create a class style and we are going to use that class style to examine inheritance when the child tag needs to overwrite the parent tag. So I am going to create a new CSS rule and I am going to create a class selector and my class selector I am going to call .boldit and you want to remember always to put the period on the front of your class styles. Now when you are using the new CSS rule dialog box, Dreamweaver would do this for your, but if you are hand-coding it obviously it doesn't so it's a really good habit to get into to always remember to put the period in front of any type of a class style that you want to create. I am going to go ahead and click OK and I am going to change my color again to a bright red and I am going to change my font weight to Bold. So anything that has the boldit style applied to it should be bold and then it should be red. So I will go ahead and click OK. Over here in my sidebar everywhere the word inheritance shows up I would like to go ahead and restyle that. So I am going to highlight the word inheritance and any time you want to apply a class style the easiest way to do that if you create the class style already defined is to use the Properties inspector. So from bottom of my page I will go down to my Properties inspector and currently the Style reads None and I kind of wish they would rename this Class because people get confused about how to apply a style or how the style apply. But if I grab the pulldown menu I can see there is the boldit style and what I really like about Dreamweaver in regards to this is that it actually renders that out, so you can see how the text is going to look. So I will click boldit and sure enough the word inheritance reformats.

Now if I look at split screen view so that we can see the code view of this, I want you to notice what happened here. So I will go and highlight the code. So notice that the word inheritance is surrounding now with the span tag, now it wasn't previously surrounded with a span tag. Dreamweaver did that for us, because in order for just the word inheritance to have the class style applied to it, obviously the class style could not have been applied to the paragraph, so it has to have some type of a tag around it. Dreamweaver uses the span tag, it's a generic inline level tag and you can go ahead and attach any class you wanted to it. So Dreamweaver will do that for you automatically. Now you can see the span tag is actually using inheritance because it has the class of boldit applied to it, which in turn is going to overwrite the parent tag, in this case the paragraph, in terms of color and font weight. So that's inheritance and again inheritance is extremely easy to understand, but when your pages get more and more complex it sometimes gets a little bit more difficult to keep track of which rules are affecting specific elements in your document. So in our next movie we will explore the concept of Specificity and we will use Dreamweaver's CSS Styles palette to help us determine the final rendering of our page elements.

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This video is part of

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Dreamweaver CS3 Beyond the Basics

102 video lessons · 38725 viewers

James Williamson
Author

 
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  1. 2m 3s
    1. Welcome
      1m 17s
    2. Using the exercise files
      46s
  2. 1h 23m
    1. Reviewing the Coding toolbar
      8m 42s
    2. Customizing the Coding toolbar
      9m 52s
    3. Taking advantage of Code Hinting
      7m 20s
    4. Using snippets and shortcuts
      11m 10s
    5. Using the Quick Tag Editor
      5m 18s
    6. Using Find and Replace
      9m 50s
    7. Regular expressions
      5m 39s
    8. Using Bridge with Dreamweaver CS3
      8m 28s
    9. Round-trip editing with Photoshop CS3
      3m 40s
    10. Leveraging image variables in Photoshop CS3
      7m 32s
    11. Integrating external variables into your workflow
      6m 16s
  3. 37m 26s
    1. Understanding the CSS Styles panel
      7m 59s
    2. Understanding the Cascade
      5m 50s
    3. Understanding Inheritance
      5m 8s
    4. Understanding Specificity
      7m 5s
    5. Managing CSS styles
      5m 4s
    6. Using Design-Time style sheets
      6m 20s
  4. 2h 19m
    1. Using the new CSS template pages
      5m 59s
    2. Understanding DIV tag structure and layout
      12m 0s
    3. Understanding the CSS box model
      10m 0s
    4. Using absolute and relative positioning
      8m 35s
    5. Understanding floating elements
      7m 9s
    6. Clearing floats
      7m 19s
    7. Using floats to control page layout
      3m 45s
    8. Building structure and assigning IDs
      10m 19s
    9. Applying basic styling to structured content
      11m 14s
    10. Positioning container elements
      11m 4s
    11. Enhancing layouts with background graphics
      11m 48s
    12. Creating faux columns with background graphics
      8m 55s
    13. Creating rounded corners with background graphics
      9m 17s
    14. Building navigation with CSS
      16m 57s
    15. Using Dreamweaver's Browser Check feature
      5m 31s
  5. 53m 22s
    1. Creating properly structured forms
      6m 30s
    2. Creating accessible forms
      6m 41s
    3. Using CSS to lay out form structure
      7m 40s
    4. Creating vertical columns for form elements
      7m 48s
    5. Adding user feedback
      5m 52s
    6. Applying advanced styling to forms
      8m 11s
    7. Client-side form validation
      4m 17s
    8. Validating forms with the Spry Validation tools
      6m 23s
  6. 1h 20m
    1. Understanding the Spry framework
      3m 43s
    2. Defining a data source for use in Spry
      3m 56s
    3. Creating a Spry table
      8m 8s
    4. Using the Spry widgets
      8m 11s
    5. Connecting various data sets
      4m 50s
    6. Understanding Spry widget structures
      7m 1s
    7. Applying custom styles to Spry widgets
      6m 24s
    8. Applying additional custom styles to Spry widgets
      8m 46s
    9. Controlling Spry widget behaviors with JavaScript
      6m 0s
    10. Controlling Spry widget animations with JavaScript
      9m 31s
    11. Creating effects with Spry behaviors
      4m 42s
    12. Hand-coding Spry
      9m 11s
  7. 1h 11m
    1. Creating a base template
      8m 6s
    2. Creating editable attributes
      6m 26s
    3. Creating a new page from a template
      7m 42s
    4. Applying a template to an existing page
      4m 36s
    5. Creating nested templates
      5m 24s
    6. Using repeating regions
      6m 34s
    7. Creating editable and non-editable optional regions
      6m 0s
    8. Using template parameters
      7m 26s
    9. Using template expressions
      9m 59s
    10. Using conditional template expressions
      8m 54s
  8. 54m 40s
    1. Examining XML structure
      2m 44s
    2. Creating an XML document
      9m 9s
    3. Using the CDATA structure
      5m 7s
    4. Creating an XSLT file
      4m 33s
    5. Binding data from an XML to an XSLT document
      5m 6s
    6. Inserting repeating regions into an XSL document
      5m 16s
    7. Creating a client-side XSL transformation
      2m 52s
    8. Styling a remote RSS feed
      7m 29s
    9. Creating a server-side XSL transformation
      5m 31s
    10. Writing XSL expressions
      6m 53s
  9. 1h 2m
    1. Overview of building dynamic websites
      1m 35s
    2. Installing PHP, MySQL, and Apache on Mac
      3m 22s
    3. Installing PHP, MySQL, and Apache on Windows
      3m 54s
    4. Creating a MySQL database
      3m 16s
    5. Defining a testing server and database bindings
      6m 14s
    6. Creating a database recordset
      4m 35s
    7. Adding dynamic content to the page
      5m 14s
    8. Creating repeating regions of dynamic content
      7m 6s
    9. Filtering database records
      7m 39s
    10. Using the Live Preview
      10m 22s
    11. Passing URL parameters
      4m 23s
    12. Dynamically generating links
      5m 18s
  10. 57m 9s
    1. Understanding behaviors
      5m 16s
    2. Installing additional behaviors
      3m 39s
    3. Planning to create a custom behavior
      3m 42s
    4. Examining existing behaviors
      5m 32s
    5. Building a behavior function
      7m 23s
    6. Creating an Action file
      6m 48s
    7. Enabling behavior functions
      9m 1s
    8. Initializing the user interface for a behavior
      3m 9s
    9. Loading behaviors in Dreamweaver
      6m 47s
    10. Testing and debugging behaviors
      5m 52s
  11. 27m 12s
    1. Running reports
      7m 41s
    2. Checking and validating links
      3m 40s
    3. Using cloaking
      5m 42s
    4. Using Check In/Check Out
      4m 3s
    5. Using Design Notes
      6m 6s
  12. 20s
    1. Goodbye
      20s

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