FindMemberPath
This method searches for a specific property in a JSON document and returns it. The property is specified according to its path in the document. 0 is returned if no corresponding property is found.
Syntax
METHOD FindMemberPath : SJsonValue
VAR_INPUT
v : SJsonValue
END_VAR
VAR_IN_OUT CONSTANT
member : STRING;
END_VAR
Return value
Name | Type |
|---|---|
FindMemberPath | SJsonValue (note possible invalidity) |
Inputs
Name | Type |
|---|---|
v | SJsonValue (note possible invalidity) |
/ Inputs/outputs
Name | Type |
|---|---|
member | STRING |
Sample call:
jsonDoc := fbJson.ParseDocument(sExistingJsonDocument);
jsonProp := fbJson.FindMemberPath(jsonDoc, sPath);Accessing nested objects works according to the scheme a/b/c, to find a variable in a JSON hierarchy. The call for the variable c of the following JSON document is:
jsonProp := fbJson.FindMemberPath(jsonDoc, 'a/b/c');{
"a":{
"b":{
"c": 123
}
}
}Support for arrays
The method supports JSON documents with arrays from TwinCAT version >3.1.4024.35. The # character can be used to access elements of an array.
jsonProp := fbJson.FindMemberPath(jsonDoc, '#1/Third#2');[
{
"First": 4
},
{
"Second": 12,
"Third": [
1,
2,
3
],
"Fourth": {
"a": true
}
},
]
The example call accesses the second element of the outer array (#1), then the third element of the array under the sub-element Third.
Treatment of special cases
Inserting the ~ character provides special treatment within a path. The following table lists the different possibilities.
Expression | Result | Example |
|---|---|---|
~0 | ~ is used as a character in the string. | Test/Hello~0123 becomes Test/Hello~123 |
~1 | The expression is replaced by the character /, which is not interpreted as a separator, but as part of the string. | Test/Hello~1123 becomes Test/Hello/123 |
~2 | The expression is replaced by the character # , which is not interpreted as an array index, but as part of the string. | Test/Hello~2123 becomes Test/Hello#123 |