Equivalence
When to use an 'equivalence' operator
The equivalence operators are useful when you want to check what a data value is.
Supported Syntax
== and !=
Examples
Not-equal operator
Use the not-equal != operator to check if the title of a widget is empty.
<b:if cond=’data:title != “”’>
<h3> <data:title /> </h3>
</b:if>
Equal operator
Use the == operator to check if you're on the home page.
<b:if cond=’data:blog.pageType == “index”’>
<p>Homepage! </p>
</b:if>
And
When to use the 'and' Operator
The and operator is most useful when you want to combine the conditions under which a Widget tag is evaluated, such as a b:if tag. This prevents you having to nest multiple b:if tags inside each other.
Supported Syntax
and and &&
Examples
Here's an example that shows when to use the and operator in a b:if tag.
Without 'and'
Without an and operator, we would need two nested b:if tags.
<b:if cond=’data:blog.pageType not in {"item","static_page"}’>
<b:if cond=’data:post.allowComments’
<b:include name='comment_count_picker' data='post' />
</b:if>
</b:if>
With 'and'
With an and operator, we can put both conditions into one b:if tag.
<b:if cond=’data:blog.pageType not in {"item","static_page"} and data:post.allowComments’>
<b:include name='comment_count_picker' data='post' />
</b:if>
Or
When to use the 'or' operator
The or operator is most useful when you want to combine several conditions, any of which would be satisfactory, under which a Widget tag such as a b:if tag is rendered. This prevents you having to repeat yourself.
Supported Syntax
or and ||
Examples
Here's an example that shows when to use the or operator in a b:if tag.
Without 'or'
With an or operator, we would need two b:if tags.
<b:if cond='data:imagePlacement == "REPLACE"’>
<b:include name="image" />
</b:if>
<b:if cond=’data:imagePlacement == “BEFORE_DESCRIPTION”’>
<b:include name=”image” />
</b:if>
With 'or'
With an or operator, we can put both conditions into one b:if tag.
<b:if cond=’data:imagePlacement == “BEFORE_DESCRIPTION” or data:imagePlacement == “REPLACE”’>
<b:include name=”image” />
</b:if>
Not
When to use the 'not' operator
The not operator is most useful when you want to operate under the condition that something is not true, like ab:if tag. This prevents you having to write an empty b:if tag just so that you can populate the b:else tag.
Supported Syntax
! and not
Examples
Here's an example that shows how to use the not operator in a b:if tag, to only show a byline on some pages.
<b:if cond=’not data:blog.pageType in {“static_page”, “index”}’>
<b:include name=”comments_byline” />
</b:if>
Ternary
When to use a Ternary operator
You can use the ternary operator to select one of two values in-line, such as on an attribute of an HTML tag.
Syntax
[condition] ? [result when true] : [result when false]
Example
Here's an example that shows how to use the ternary operator in an HTML div tag to apply a different CSS class when comments are allowed, then when they're not allowed.
<div expr:class=’data:post.
</div>
Membership
When to use a Membership operator
You can use the membership operator to check if a value is one of several possible values. This prevents you having to have several or conditions with equivalence operators.
Syntax
Define a set using { } or [ ], then apply the in and contains operators.
Examples
Here's an example that shows how to use the contains membership operator to check if the page type is a static page, or a single post.
<b:if cond=’{“item”, “static_page”} contains data:blog.pageType’>
<p>Single Post or Page! </p>
</div>
Here's an example that shows how to use the in membership operator to check if the page type is the home page, or an archive page.
<b:if cond=’data:blog.pageType in [“index”, “archive”]’>
<p>Homepage or Archive Page! </p>
</div>
Lambda
When to use a Lambda expression
Lambda expressions are useful when you want to check if a condition is true for one, all, or none of the items in a set. You can also use it to filter a set of items, or map a set of items to a new set.
Syntax
[set of items] [lambda operator] ([lambda expression])
Lambda expressions have the format
[variable name] => [expression]
Note that variable name can be any string of letters. Generally, for brevity, we choose a relevant letter, like x, but it could be a longer name like label or myVariableName.
As an example, an expression for determining the count of posts with at least one comment would be:
data:posts count (p => p.numComments > 0)
In this example, data:posts is the set, count is the lambda operator, and p => p.numComments > 0 is the lambda expression. The count operator counts the number of items in the set data:posts for which the expression p => p.numComments > 0 is true, i.e. the number of posts with at least one comment.
As another example, to add a flower image if the post is labelled ‘Flower’:
<img src=’/img/flower.jpg’ />
</b:if>
Lambda Operators
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Resize
When to use image resize operators
The image resize operators are useful when you want to ensure that an image is displayed in a suitable size. Generally this will be used to get a cropped thumbnail of an image, or to create a responsive image for a mobile-friendly template.
Syntax
Resize a single image url
resizeImage(imageUrl, newSize, optionalRatio)
The resizeImage operator takes 3 parameters:
- imageUrl - The original URL of the resizable image.
- newSize - The new width of the image
- (optional) ratio - The integer ratio of width to height for the resized image, e.g. “1:1” or “4:3”
Notes
- If the imageUrl parameter is not a resizable image, the resizeImage function will return the original imageUrl.
- The ratio must be integer numbers.
- If the ratio is provided, the image will be cropped to those exact dimensions.
Example
<img expr:src=’resizeImage(data:
Create a responsive image srcset
sourceSet(imageUrl, newSizes, optionalRatio)
The sourceSet operator takes 3 parameters:
- imageUrl - The original URL of the resizable image.
- newSizes - An array of new widths of the image
- (optional) ratio - The integer ratio of width to height for the resized image, e.g. “1:1” or “4:3”
Notes
- If the imageUrl parameter is not a resizable image, the sourceSet function will return an empty string
- The ratio must be integer numbers
- If the ratio is provided, the image will be cropped to those exact dimensions
Example
<img expr:src=’data:post.firstImageUrl’ expr:srcset=’sourceSet(data: post.firstImageUrl, [128, 256, 512])’ />
Sumber : https://productforums.google.com/forum/#!topic/blogger/59LGf47pPP8
Tidak ada komentar:
Posting Komentar