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Ternary Operator ? x : y
This operator is used to simplify the following syntax:
| Code Block |
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| language | groovy |
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| title | Case 1: complicated Complicated syntax |
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if (product.label != null && product.label.length() > 0) {
return product.label
} else {
return 'N/A'
} |
You can rewrite the above statement using the ternary operator:
| Code Block |
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| title | Case 2: simplified Simplified syntax |
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return (product.label != null && product.label.length() > 0) ? product.label : 'N/A' |
And then simplify it even more since not-empty check in Groovy can be done like this:
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| title | Case 3: simplified Simplified syntax |
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return product.label ? product.label : 'N/A' |
Elvis Operator ?:
This operator is used to provide a default fallback value if certain variable is empty or null. If the expression in the middle of the ternary operator is identical to it's its first expression, you should simplify the return statement from the previous example above using ?: operator:
| Code Block |
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| language | groovy |
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| title | Case 1: preferred Preferred syntax |
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return product.label ?: 'N/A' // Elvis operator |
This can be useful if you need, for example, to always return a date when target date is not set:
| Code Block |
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| language | groovy |
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| title | Case 2: common Common example - target date |
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date = api.targetDate() ?: new Date() // if target date is null, return the current date |
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| Code Block |
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| language | groovy |
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| title | Case 3: common Common example - input parameter adjustment |
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lookback = api.decimalUserEntry('Look-back period (default: 20)') ?: 20 // if the user doesn't specify the look-back period, it will default to 20 |
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| Info |
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In case you wonder why this is called Elvis operator:  ?: → rotate 90° right →  →  |
Safe Navigation Operator ?.
This operator provides a not-null check before accessing a value from object. Whenever you access object's attribute or method you should check for a non-null reference like this:
| Code Block |
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| language | groovy |
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| title | Case 1: functionally Functionally correct, but complicated syntax |
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if (date) {
return date.format('yyyy-MM-dd')
}
return null |
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| Code Block |
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| language | groovy |
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| title | Case 2: simplified Simplified syntax |
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|
return date ? date.format('yyyy-MM-dd') : null |
...
| Code Block |
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| language | groovy |
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| title | Case 3: preffered Preffered syntax |
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return date?.format('yyyy-MM-dd') |
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| Code Block |
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| language | groovy |
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| title | Case 4: multiple Multiple occurences for safe navigation operator |
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return product?.attribute21?.toBigDecimal() |
Spread Operator *
Imagine the following api.find with many filters:
| Code Block |
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| language | groovy |
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| title | Case 1: functionally Functionally correct, but complicated syntax |
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api.find('P', Filter.equal("attribute1", "P"), Filter.or(Filter.equal("attribute2", "Red"), Filter.equal("attribute2", "Green"), Filter.equal("attribute2", "Blue")),Filter.equal("attribute3", 123)) |
It works fine, but is it's very difficult to read right? Therefore a the following syntax is preferred:
| Code Block |
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| language | groovy |
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| title | Case 2: preferred Preferred syntax, easy to read |
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|
def filter = Filter.and(
Filter.equal("attribute1", "P"),
Filter.or(
Filter.equal("attribute2", "Red"),
Filter.equal("attribute2", "Green"),
Filter.equal("attribute2", "Blue"),
),
Filter.equal("attribute3", 123),
)
api.find('P', filter) |
It is now much easier to read what the filter is supposed to return and also distinguish the priorities between AND and OR, right?
Sometimes you may find the following syntax that has identical meaning:
| Code Block |
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| language | groovy |
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| title | Case 3: alternative Alternative syntax, easy to read |
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def filters = [
Filter.equal("attribute1", "P"),
Filter.or(
Filter.equal("attribute2", "Red"),
Filter.equal("attribute2", "Green"),
Filter.equal("attribute2", "Blue"),
),
Filter.equal("attribute3", 123),
]
// notice the * char. This will unwrap each item of the collection and pass it to the method as a separate parameter
api.find('P', *filters) |
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| Code Block |
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| language | groovy |
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| title | Case 4: wrong Wrong syntax - missing * |
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api.find('P', filters) |
Groovy compiler will throw an a compilation error since no version of api.find() does accept accepts a collection as argument but only a variable number of Filter objects:
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No signature of method: net.pricefx.formulaengine.scripting.SandboxAPI.find() is applicable for argument types: (java.lang.String, java.util.ArrayList) values: [P, [`attribute1` = "P", (`attribute2` = "Red" or `attribute2` = "Green" or `attribute2` = "Blue"), ...]]
Possible solutions: find(), find(java.lang.String, [Lcom.googlecode.genericdao.search.Filter;), find(java.lang.String, int, [Lcom.googlecode.genericdao.search.Filter;), find(groovy.lang.Closure), find(java.lang.String, int, java.lang.String, [Lcom.googlecode.genericdao.search.Filter;), uuid() |
Spaceship Operator <=>
This operator delegates to the compareTo method of the left-side operand and passes it the right-side operand.
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It is best when mixed with a sort methodsort method.
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def competitors = api.productExtension('Competition')
def sortedByName = competitors .sort { a, b -> return a.attribute1 <=> b.attribute1 } // assuming attribute1 is the name of the competitor |
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