I've "inherited" some Tcl code, and while I worked through some tutorials and can make sense out of the language, my own Tcl constructs lack a certain... finesse.
For example, I have this code:
puts "Column 'name': [ $queryRs getString name ]"
$queryRs is the result set of a SQL query. The [ $queryRs getString name ] construct retrieves the content of the table column "name" from the current row in the result set. If the database field is NULL, the puts does not print anything.
I would like to print a "default" string instead, i.e. if [ $queryRs getString name ] results in nothing, I'd like to replace it with "--".
Now, I could do something like this:
set nameVar "[ $queryRs getString name ]"
if { [ string length $nameVar ] == 0 } {
set nameVar "--"
}
puts "Column 'name': $nameVar"
But there has to be a more compact solution, something that can be done inline instead of adding four lines and a temporary variable. Help, please?
Two things.
First, Tcl doesn't have a notion of NULL (nil, undefined or whatever) value, and when you want to simulate such a value you have to either use a variable and test for its existence or use an entry in an array of dictionary and test for its existence, too. If such a variable/entry exists, then the value is defined, otherwise it's not.
Unfortunately, the creator of your inherited code apparently did not care about the case where a variable can be NULL so NULLs are indistinguishable from variables having default values (an empty string).
Next, you can use a helper procedure to do what you need:
proc ValueOrDef {val {def --}} {
expr {$val ne "" ? $val : $def}
}
and then go like this:
puts [ValueOrDef [$queryRs getString name]]
puts [ValueOrDef [$queryRs getString name] "some other default"]
You could use the x?y:z construct of the expr command. x is the condition, y is the alternative if the condition is met and z is the alternative if x is not met.
E.g. (but still with a temporary variable):
set nameVar [ $queryRs getString name ]
puts "Column 'name': [expr {[string length $nameVar]>0 ? $nameVar : "--"}]"
Related
I have the following code:
$DatabaseSettings = #();
$NewDatabaseSetting = "" | select DatabaseName, DataFile, LogFile, LiveBackupPath;
$NewDatabaseSetting.DatabaseName = "LiveEmployees_PD";
$NewDatabaseSetting.DataFile = "LiveEmployees_PD_Data";
$NewDatabaseSetting.LogFile = "LiveEmployees_PD_Log";
$NewDatabaseSetting.LiveBackupPath = '\\LiveServer\LiveEmployeesBackups';
$DatabaseSettings += $NewDatabaseSetting;
When I try to use one of the properties in a string execute command:
& "$SQlBackupExePath\SQLBackupC.exe" -I $InstanceName -SQL `
"RESTORE DATABASE $DatabaseSettings[0].DatabaseName FROM DISK = '$tempPath\$LatestFullBackupFile' WITH NORECOVERY, REPLACE, MOVE '$DataFileName' TO '$DataFilegroupFolder\$DataFileName.mdf', MOVE '$LogFileName' TO '$LogFilegroupFolder\$LogFileName.ldf'"
It tries to just use the value of $DatabaseSettings rather than the value of $DatabaseSettings[0].DatabaseName, which is not valid.
My workaround is to have it copied into a new variable.
How can I access the object's property directly in a double-quoted string?
When you enclose a variable name in a double-quoted string it will be replaced by that variable's value:
$foo = 2
"$foo"
becomes
"2"
If you don't want that you have to use single quotes:
$foo = 2
'$foo'
However, if you want to access properties, or use indexes on variables in a double-quoted string, you have to enclose that subexpression in $():
$foo = 1,2,3
"$foo[1]" # yields "1 2 3[1]"
"$($foo[1])" # yields "2"
$bar = "abc"
"$bar.Length" # yields "abc.Length"
"$($bar.Length)" # yields "3"
PowerShell only expands variables in those cases, nothing more. To force evaluation of more complex expressions, including indexes, properties or even complete calculations, you have to enclose those in the subexpression operator $( ) which causes the expression inside to be evaluated and embedded in the string.
#Joey has the correct answer, but just to add a bit more as to why you need to force the evaluation with $():
Your example code contains an ambiguity that points to why the makers of PowerShell may have chosen to limit expansion to mere variable references and not support access to properties as well (as an aside: string expansion is done by calling the ToString() method on the object, which can explain some "odd" results).
Your example contained at the very end of the command line:
...\$LogFileName.ldf
If properties of objects were expanded by default, the above would resolve to
...\
since the object referenced by $LogFileName would not have a property called ldf, $null (or an empty string) would be substituted for the variable.
Documentation note: Get-Help about_Quoting_Rules covers string interpolation, but, as of PSv5, not in-depth.
To complement Joey's helpful answer with a pragmatic summary of PowerShell's string expansion (string interpolation in double-quoted strings ("...", a.k.a. expandable strings), including in double-quoted here-strings):
Only references such as $foo, $global:foo (or $script:foo, ...) and $env:PATH (environment variables) can directly be embedded in a "..." string - that is, only the variable reference itself, as a whole is expanded, irrespective of what follows.
E.g., "$HOME.foo" expands to something like C:\Users\jdoe.foo, because the .foo part was interpreted literally - not as a property access.
To disambiguate a variable name from subsequent characters in the string, enclose it in { and }; e.g., ${foo}.
This is especially important if the variable name is followed by a :, as PowerShell would otherwise consider everything between the $ and the : a scope specifier, typically causing the interpolation to fail; e.g., "$HOME: where the heart is." breaks, but "${HOME}: where the heart is." works as intended.
(Alternatively, `-escape the :: "$HOME`: where the heart is.", but that only works if the character following the variable name wouldn't then accidentally form an escape sequence with a preceding `, such as `b - see the conceptual about_Special_Characters help topic).
To treat a $ or a " as a literal, prefix it with escape char. ` (a backtick); e.g.:
"`$HOME's value: $HOME"
For anything else, including using array subscripts and accessing an object variable's properties, you must enclose the expression in $(...), the subexpression operator (e.g., "PS version: $($PSVersionTable.PSVersion)" or "1st el.: $($someArray[0])")
Using $(...) even allows you to embed the output from entire commands in double-quoted strings (e.g., "Today is $((Get-Date).ToString('d')).").
Interpolation results don't necessarily look the same as the default output format (what you'd see if you printed the variable / subexpression directly to the console, for instance, which involves the default formatter; see Get-Help about_format.ps1xml):
Collections, including arrays, are converted to strings by placing a single space between the string representations of the elements (by default; a different separator can be specified by setting preference variable $OFS, though that is rarely seen in practice) E.g., "array: $(#(1, 2, 3))" yields array: 1 2 3
Instances of any other type (including elements of collections that aren't themselves collections) are stringified by either calling the IFormattable.ToString() method with the invariant culture, if the instance's type supports the IFormattable interface[1], or by calling .psobject.ToString(), which in most cases simply invokes the underlying .NET type's .ToString() method[2], which may or may not give a meaningful representation: unless a (non-primitive) type has specifically overridden the .ToString() method, all you'll get is the full type name (e.g., "hashtable: $(#{ key = 'value' })" yields hashtable: System.Collections.Hashtable).
To get the same output as in the console, use a subexpression in which you pipe to Out-String and apply .Trim() to remove any leading and trailing empty lines, if desired; e.g.,
"hashtable:`n$((#{ key = 'value' } | Out-String).Trim())" yields:
hashtable:
Name Value
---- -----
key value
[1] This perhaps surprising behavior means that, for types that support culture-sensitive representations, $obj.ToString() yields a current-culture-appropriate representation, whereas "$obj" (string interpolation) always results in a culture-invariant representation - see this answer.
[2] Notable overrides:
• The previously discussed stringification of collections (space-separated list of elements rather than something like System.Object[]).
• The hashtable-like representation of [pscustomobject] instances (explained here) rather than the empty string.
#Joey has a good answer. There is another way with a more .NET look with a String.Format equivalent, I prefer it when accessing properties on objects:
Things about a car:
$properties = #{ 'color'='red'; 'type'='sedan'; 'package'='fully loaded'; }
Create an object:
$car = New-Object -typename psobject -Property $properties
Interpolate a string:
"The {0} car is a nice {1} that is {2}" -f $car.color, $car.type, $car.package
Outputs:
# The red car is a nice sedan that is fully loaded
If you want to use properties within quotes follow as below. You have to use $ outside of the bracket to print property.
$($variable.property)
Example:
$uninstall= Get-WmiObject -ClassName Win32_Product |
Where-Object {$_.Name -like "Google Chrome"
Output:
IdentifyingNumber : {57CF5E58-9311-303D-9241-8CB73E340963}
Name : Google Chrome
Vendor : Google LLC
Version : 95.0.4638.54
Caption : Google Chrome
If you want only name property then do as below:
"$($uninstall.name) Found and triggered uninstall"
Output:
Google Chrome Found and triggered uninstall
I have the following code:
$DatabaseSettings = #();
$NewDatabaseSetting = "" | select DatabaseName, DataFile, LogFile, LiveBackupPath;
$NewDatabaseSetting.DatabaseName = "LiveEmployees_PD";
$NewDatabaseSetting.DataFile = "LiveEmployees_PD_Data";
$NewDatabaseSetting.LogFile = "LiveEmployees_PD_Log";
$NewDatabaseSetting.LiveBackupPath = '\\LiveServer\LiveEmployeesBackups';
$DatabaseSettings += $NewDatabaseSetting;
When I try to use one of the properties in a string execute command:
& "$SQlBackupExePath\SQLBackupC.exe" -I $InstanceName -SQL `
"RESTORE DATABASE $DatabaseSettings[0].DatabaseName FROM DISK = '$tempPath\$LatestFullBackupFile' WITH NORECOVERY, REPLACE, MOVE '$DataFileName' TO '$DataFilegroupFolder\$DataFileName.mdf', MOVE '$LogFileName' TO '$LogFilegroupFolder\$LogFileName.ldf'"
It tries to just use the value of $DatabaseSettings rather than the value of $DatabaseSettings[0].DatabaseName, which is not valid.
My workaround is to have it copied into a new variable.
How can I access the object's property directly in a double-quoted string?
When you enclose a variable name in a double-quoted string it will be replaced by that variable's value:
$foo = 2
"$foo"
becomes
"2"
If you don't want that you have to use single quotes:
$foo = 2
'$foo'
However, if you want to access properties, or use indexes on variables in a double-quoted string, you have to enclose that subexpression in $():
$foo = 1,2,3
"$foo[1]" # yields "1 2 3[1]"
"$($foo[1])" # yields "2"
$bar = "abc"
"$bar.Length" # yields "abc.Length"
"$($bar.Length)" # yields "3"
PowerShell only expands variables in those cases, nothing more. To force evaluation of more complex expressions, including indexes, properties or even complete calculations, you have to enclose those in the subexpression operator $( ) which causes the expression inside to be evaluated and embedded in the string.
#Joey has the correct answer, but just to add a bit more as to why you need to force the evaluation with $():
Your example code contains an ambiguity that points to why the makers of PowerShell may have chosen to limit expansion to mere variable references and not support access to properties as well (as an aside: string expansion is done by calling the ToString() method on the object, which can explain some "odd" results).
Your example contained at the very end of the command line:
...\$LogFileName.ldf
If properties of objects were expanded by default, the above would resolve to
...\
since the object referenced by $LogFileName would not have a property called ldf, $null (or an empty string) would be substituted for the variable.
Documentation note: Get-Help about_Quoting_Rules covers string interpolation, but, as of PSv5, not in-depth.
To complement Joey's helpful answer with a pragmatic summary of PowerShell's string expansion (string interpolation in double-quoted strings ("...", a.k.a. expandable strings), including in double-quoted here-strings):
Only references such as $foo, $global:foo (or $script:foo, ...) and $env:PATH (environment variables) can directly be embedded in a "..." string - that is, only the variable reference itself, as a whole is expanded, irrespective of what follows.
E.g., "$HOME.foo" expands to something like C:\Users\jdoe.foo, because the .foo part was interpreted literally - not as a property access.
To disambiguate a variable name from subsequent characters in the string, enclose it in { and }; e.g., ${foo}.
This is especially important if the variable name is followed by a :, as PowerShell would otherwise consider everything between the $ and the : a scope specifier, typically causing the interpolation to fail; e.g., "$HOME: where the heart is." breaks, but "${HOME}: where the heart is." works as intended.
(Alternatively, `-escape the :: "$HOME`: where the heart is.", but that only works if the character following the variable name wouldn't then accidentally form an escape sequence with a preceding `, such as `b - see the conceptual about_Special_Characters help topic).
To treat a $ or a " as a literal, prefix it with escape char. ` (a backtick); e.g.:
"`$HOME's value: $HOME"
For anything else, including using array subscripts and accessing an object variable's properties, you must enclose the expression in $(...), the subexpression operator (e.g., "PS version: $($PSVersionTable.PSVersion)" or "1st el.: $($someArray[0])")
Using $(...) even allows you to embed the output from entire commands in double-quoted strings (e.g., "Today is $((Get-Date).ToString('d')).").
Interpolation results don't necessarily look the same as the default output format (what you'd see if you printed the variable / subexpression directly to the console, for instance, which involves the default formatter; see Get-Help about_format.ps1xml):
Collections, including arrays, are converted to strings by placing a single space between the string representations of the elements (by default; a different separator can be specified by setting preference variable $OFS, though that is rarely seen in practice) E.g., "array: $(#(1, 2, 3))" yields array: 1 2 3
Instances of any other type (including elements of collections that aren't themselves collections) are stringified by either calling the IFormattable.ToString() method with the invariant culture, if the instance's type supports the IFormattable interface[1], or by calling .psobject.ToString(), which in most cases simply invokes the underlying .NET type's .ToString() method[2], which may or may not give a meaningful representation: unless a (non-primitive) type has specifically overridden the .ToString() method, all you'll get is the full type name (e.g., "hashtable: $(#{ key = 'value' })" yields hashtable: System.Collections.Hashtable).
To get the same output as in the console, use a subexpression in which you pipe to Out-String and apply .Trim() to remove any leading and trailing empty lines, if desired; e.g.,
"hashtable:`n$((#{ key = 'value' } | Out-String).Trim())" yields:
hashtable:
Name Value
---- -----
key value
[1] This perhaps surprising behavior means that, for types that support culture-sensitive representations, $obj.ToString() yields a current-culture-appropriate representation, whereas "$obj" (string interpolation) always results in a culture-invariant representation - see this answer.
[2] Notable overrides:
• The previously discussed stringification of collections (space-separated list of elements rather than something like System.Object[]).
• The hashtable-like representation of [pscustomobject] instances (explained here) rather than the empty string.
#Joey has a good answer. There is another way with a more .NET look with a String.Format equivalent, I prefer it when accessing properties on objects:
Things about a car:
$properties = #{ 'color'='red'; 'type'='sedan'; 'package'='fully loaded'; }
Create an object:
$car = New-Object -typename psobject -Property $properties
Interpolate a string:
"The {0} car is a nice {1} that is {2}" -f $car.color, $car.type, $car.package
Outputs:
# The red car is a nice sedan that is fully loaded
If you want to use properties within quotes follow as below. You have to use $ outside of the bracket to print property.
$($variable.property)
Example:
$uninstall= Get-WmiObject -ClassName Win32_Product |
Where-Object {$_.Name -like "Google Chrome"
Output:
IdentifyingNumber : {57CF5E58-9311-303D-9241-8CB73E340963}
Name : Google Chrome
Vendor : Google LLC
Version : 95.0.4638.54
Caption : Google Chrome
If you want only name property then do as below:
"$($uninstall.name) Found and triggered uninstall"
Output:
Google Chrome Found and triggered uninstall
I have this list:
service_name_status=[a-service=INSTALL, b-service=UPGRADE, C-service=UPGRADE, D-service=INSTALL]
And I need to iterate through this list so the first element will be the value of a parameter called "SERVICE_NAME" and the second element will be the value of a parameter called "HELM_COMMAND",
after asserting those values to the parameters I will run my command that uses those parameters and then continue the next items on the list which should replace the values of the parameters with items 3 and 4 and so on.
So what I am looking for is something like that:
def service_name_status=[a-service=INSTALL, b-service=UPGRADE, C-service=UPGRADE, D-service=INSTALL]
def SERVICE_NAME
def HELM_COMMAND
for(x in service_name_status){
SERVICE_NAME=x(0,2,4,6,8...)
HELM_COMMAND=x(1,3,5,7,9...)
println SERVICE_NAME=$SERVICE_NAME
println HELM_COMMAND=$HELM_COMMAND
}
the output should be:
SERVICE_NAME=a-service
HELM_COMMAND=INSTALL
SERVICE_NAME=b-service
HELM_COMMAND=UPGRADE
SERVICE_NAME=c-service
HELM_COMMAND=UPGRADE
SERVICE_NAME=d-service
HELM_COMMAND=INSTALL
and so on...
I couldn't find anything that takes any other element in groovy, any help will be appreciated.
The collection you want is a Map, not a List.
Take note of the quotes in the map, the values are strings so you need the quotes or it won't work. You may have to change that at the source where your data comes from.
I kept your all caps variable names so you will feel at home, but they are not the convention.
Note the list iteration with .each(key, value)
This will work:
Map service_name_status = ['a-service':'INSTALL', 'b-service':'UPGRADE', 'C-service':'UPGRADE', 'D-service':'INSTALL']
service_name_status.each {SERVICE_NAME, HELM_COMMAND ->
println "SERVICE_NAME=${SERVICE_NAME}"
println "HELM_COMMAND=${HELM_COMMAND}"
}
EDIT:
The following can be used to convert that to a map. Be careful, the replaceAll part is fragile and depends on the data to always look the same.
//assuming you can have it in a string like this
String st = "[a-service=INSTALL, b-service=UPGRADE, C-service=UPGRADE, D-service=INSTALL]"
//this part is dependent on format
String mpStr = st.replaceAll(/\[/, "['")
.replaceAll(/=/, "':'")
.replaceAll(/]/, "']")
.replaceAll(/, /, "', '")
println mpStr
//convert the properly formatted string to a map
Map mp = evaluate(mpStr)
assert mp instanceof java.util.LinkedHashMap
I have 2 variables json array
variable1 =
[
{
"CurrentDate": "2019-05-11",
"CurrentTime": "01:09:14",
"tablename": "A"
},
{
"CurrentDate": "2019-05-11",
"CurrentTime": "01:11:14",
"tablename": "Z"
}
]
variable2 =
[
{
"A": "Topic1"
},
{
"Z": "Topic2"
}
]
Now I want to compare tablename value with variable2 key and if it matches pass variable2 value to next step.
For example, in variable1 for each loop it will take tablename value A checks with variable2 array each element and key matches for A then I need to pass its value as Topic1 to next step or assign a value to global variable. Same happens for all the elements one by one.
I tried using 2 foreach but unable to assign values. How can I write an expression to match value and assign global value after match to variable?
If this is not possible I will modify variable2 like
variable2 =
[
"A" , "B"
] and add equal expression like "equals": [
"#items('For_each')?['tablename']",
"#items('For_each_2')"
]
You can now run code inside a logic app (limited to javascript for the moment):
See the documentation for more information:
Add and run code snippets by using inline code in Azure Logic Apps.
This should do the trick for you.
In this code snippet, fields-types in the end is modified by the to-camel-case function, vs. being passed as a local variable to the parent function:
fields-types: ["First Name" "string" "Last Name" "string" "Age" "int"]
to-camel-case: function [name] [
name/1: lowercase name/1
replace/all name space ""
]
fill-template-body: func [
field-labels-types [block!] /local vars fields-names-types
] [
vars: [member-name member-type]
field-names-types: copy []
foreach [field-label field-type] field-labels-types [
append field-names-types to-camel-case field-label
append field-names-types field-type
]
]
fill-template-body fields-types
Execution gives:
>> fill-template-body fields-types
== ["firstName" "string" "lastName" "string" "age" "int"]
>> fields-types
== ["firstName" "string" "lastName" "string" "age" "int"]
>>
Whereas I would want that fields-types to stay invariant:
fields-types: ["First Name" "string" "Last Name" "string" "Age" "int"]
Of course I can try to circumvent this by modifying to-camel-case to use a copy of name, but that is not something I think I should have to do.
Is there something like the var and val keywords in Scala?
Variable is an ugly word in REBOL, everything - even words - are values. This isn't some semantic newspeak, it's helpful in understanding the way in which REBOL flows.
I think of values as being contained within one giant array in memory, where REBOL (the language) uses words and their contexts to reference and interact with the values. Most REBOL functions operate without duplicating these values:
head lowercase next uppercase str: "abcd"
remove back tail str
This is one of REBOL's most efficient features - you don't need copies for intermediary processes, to require such is wasteful. Think of that array growing where every time you use replace, uppercase or to-camel-case a value is duplicated. Whole processes can be built on the premise of modification rather than duplication - indeed a context can be built without necessarily having to return a value:
remove-spaces: use [space mark][
space: charset " ^-"
[any [mark: space (remove mark) | skip]]
]
parse/all str: "Should Be No Spaces" remove-spaces
The trick then becomes knowing where to copy values, and I think happens to intersect with REBOL's gift for concise expression:
parse/all link: copy title: "An Article on REBOL" remove-spaces
print ["(" link ")" title]
to-camel-case copy field-label
And of course, modification has its limitations. Sometimes it is cleaner building from scratch.
Your camel case function operates on the original value so if you want to preserve the original value, you need to copy it, and return the altered value. Since your function acts on a template it needs to copy the template right??
So, something like this should work:
fill-template-body: func[ labels [block!] /local field-labels-types vars fields-names-types][
field-labels-types: copy labels
..