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* Modify SetWidget to include use to set global variables. * Make sample variables easier to read. * Change text to indicate use of pragma whitespace trim. * Make compliant with 5.3.1 (?) release
139 lines
5.4 KiB
Plaintext
139 lines
5.4 KiB
Plaintext
caption: set
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created: 20131115182700000
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modified: 20230720174707977
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tags: Widgets
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title: SetWidget
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type: text/vnd.tiddlywiki
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! Introduction
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The set variable widget assigns a value to a specified [[variable|Variables]]. The new value of the variable is available to the content within the set variable widget.
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! Content and Attributes
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The content of the `<$set>` widget is the scope for the value assigned to the variable.
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|!Attribute |!Description |
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|name |The name of the variable to assign (defaults to "currentTiddler") |
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|value |The value to assign to the variable if the <<.attr filter>> attribute is missing or not empty |
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|tiddler |<<.from-version "5.1.15">> Optional title of the tiddler from which to read the value |
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|subtiddler |<<.from-version "5.1.16">> Optionally specifies the title of a subtiddler within a plugin tiddler identified by the ''tiddler'' attribute |
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|field |<<.from-version "5.1.15">> Optional field of the tiddler from which to read the value (only used if ''tiddler'' is used) |
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|index |<<.from-version "5.1.15">> Optional index of the tiddler from which to read the value (only used if ''tiddler'' is used) |
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|filter |An optional filter to be evaluated and assigned to the variable (see "Filtered List Variable Assignment" below). The variable can be used with the <<.olink enlist>> operator |
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|select |<<.from-version "5.1.14">> An optional zero-based index of the item to return from the filter output (see below) |
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|emptyValue |The value to assign to the variable if the specified value is missing or empty (see below) |
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<<.tip """If the value of your variable is enclosed in double square brackets this might indicate that you are returning a list of values from the filter. To use a single title from the filter output without the double square brackets see ''Filtered Item Variable Assignment'' below.""">>
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! Examples
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!! Simple Variable Assignment
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The simplest way of using set variable widget assigns a string to a variable. The following example assigns a literal string
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name="myVariable" value="Some text">
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<$text text=<<myVariable>>/>
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</$set>' />
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<<<
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Both the name and value attributes can be transcluded. For example:
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name=anotherVariable value="myVariable">
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<$set name=<<anotherVariable>> value={{$:/language/DefaultNewTiddlerTitle}}>
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<$text text=<<myVariable>>/>
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</$set>
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</$set>' />
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<<<
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!! Conditional Variable Assignment
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This form of the set variable widget chooses one of two specified values according to whether a filter evaluates to an empty list. Here's an example that sets a variable according to whether the current tiddler is called "myMagicTitle":
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src="""<$set name="myVariable" filter="[all[current]field:title[myMagicTitle]]" value="It's magic" emptyValue="It's not magic">
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<$text text=<<myVariable>>/>
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</$set>""" />
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<<<
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!! Filtered List Variable Assignment
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This form of the set variable widget evaluates the filter and assigns the result to the variable as a space-separated list (using double square brackets for titles containing spaces).
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<<.warning """The [[Title List]] format cannot reliably represent items that contain certain specific character sequences such as `]] `. Thus it should not be used where there is a possibility of such sequences occurring.""">>
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name="myVariable" filter="[tag[HelloThere]]">
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<$text text=<<myVariable>>/>
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</$set>' />
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<<<
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!! Filtered Item Variable Assignment Single Element
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<<.from-version "5.1.14">> This form of the set variable widget evaluates the filter and assigns the specified result to the variable as a single item (ie, not using double square brackets for titles containing spaces).
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name="myVariable" filter="[tag[HelloThere]]" select="0">
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<$text text=<<myVariable>>/>
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</$set>'/>
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<<<
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!! Transcluded Variable Assignment
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<<.from-version "5.1.15">> This form of the set variable widget obtains the value to assign to the variable from a value in a tiddler field or index. For example:
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name="myVariable" tiddler="HelloThere" field="list">
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<$text text=<<myVariable>>/>
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</$set>'/>
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<<<
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The example above could also be written as `<$set name="myVariable" value={{HelloThere!!list}}>`. The advantage of using the ''tiddler'' attribute is that the tiddler title and field or index can themselves be computed. For example:
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<<<
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<$macrocall $name='wikitext-example-without-html'
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src='<$set name="myTiddler" value="HelloThere">
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<$set name="myVariable" tiddler=<<myTiddler>> field={{$:/docs/anyField!!field}}>
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<$text text=<<myVariable>>/>
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</$set>
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</$set>'/>
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<<<
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!! Using the Set Widget to Create Global Variables
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There are times when it makes sense to use the features of the [[SetWidget]] rather than procedures or functions to create global variables. This can be accomplished by placing the set variable widget in a tiddler that is tagged [[$:/tags/Global|SystemTag: $:/tags/Global]]. If multiple variables are required, the set variable widget can be nested as shown here:
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<<<
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<div class="doc-example">
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```
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<$set name="myGlobalVariable" value="I am global">
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<$set name="myOtherGlobalVariable" value="I am also a global variable.">
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</$set>
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</$set>
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```
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</div>
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<<<
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