VBScript Reference Manual for InduSoft Web Studio - ICP DAS

More documents

Recommendations

Info

VBScript Reference ManualInduSoft Web StudioVBScript User-Defined Class ObjectsTo define a user-defined Class Object, you use the Class statement to declare a class. The End Classstatement defines the termination of the Class. Together, these statements form a Class construct, orClass block. E.g.Class objName‘ Place the Class variables, Properties and Methods hereEnd ClassIn this syntax, objName is the name given to the Class Object. The class object name must followstandard VBScript variable naming conventions. Class Objects are usually declared in the variabledefinition sections. You can have multiple Class blocks in a single VBScript file, but each block mustcontain the Class …End Class statements. Classes cannot be nested.Once you have defined the Class Object, you need to create an instance of the Class, similar to howother objects are created. When the Class Object is instantiated, memory is allocated for the ClassObject. The Set statement is used with the New keyword to assign an instance of the class to avariable. With VBScript, this is the only time the New keyword is used (i.e. to instantiate a user-definedClass). E.g.Dim MyObjSet MyObj = New objNameThe Object name MyObj is the Object variable name, and must follow standard VBScript variablenaming conventions. The Object variable name is a reference (address) of the Object stored inmemory, it is not the Object itself.Inside the Class block, any Class variables, Properties, Methods and Events can be defined by thedeveloper. The developer does not have to use all of the capabilities of the Class construct, i.e. Classescan be created without Methods or Properties. The design of the Class Object is completely up to thedeveloper.Class variables are created within the Class structure by using the Dim, Public, or Private statements.Variables defined within the Class structure by any of these statements must follow the standardVBScript variable naming conventions. Variables can be simple variables or arrays. E.g.Class classNameDim var1, var2Public var3, var4Private var5, var6End ClassThe choice of the Dim, Public, or Private statements determine whether the variable is accessibleoutside of the Class Object. Variables are public by default, i.e. they are accessible outside of the ClassObject. Both the Dim and the Public statements create public variables, while the Private statementcreates variables that are not public. As a general rule, it is good programming practice to make allClass variables private, since the developer will want to tightly control when these variables arechanged.VBScript does not support Class-level Constants, i.e. named constants declared at the Class level. Youcannot use the Const statement at the Class-level so that a constant can be used throughout a Class,but you can use the Const statement within a Property or Method. However, the constant will only havelocal scope within the Property or Method.24 InduSoft, Ltd.
InduSoft Web StudioVBScript Reference ManualClass Object variables are accessible to VBScript code outside the Class through Class Properties.Class Properties “wrap” the Private variables of a Class. Inside the Class block, the Properties aredefined by Property Get [|Let|Set] … End Property statement(s). For VBScript code outside theClass, the Property is accessed by referencing the Object Name.Property.There are different type of Class Properties, depending on whether the Class variable is to be read,written to, or the Class variable is itself a Class Object. These Properties can be declared Public orPrivate.Property GetThe Property Get procedure is used to access (return) private variables inside of the Classstructure that are used as a read-only Property, or the read portion of a read-write Property. ForVBScript code outside the Class, this type of Class Object Property is generally assigned to avariable or used in a conditional expression. The Property Get procedure returns a value to thecalling code, and is general not used with any arguments. [Note: VBScript will let you addarguments to the Property Get procedure, but if you do so you must add the additionalargument to the corresponding Property Let or Property Set procedure, since PropertyLet/Property Set must have one more argument than the corresponding Property Getprocedure. It is generally considered bad programming form to have arguments in the PropertyGet procedure].Property LetThe Property Let procedure is used to access (assign) private variables inside of the Classstructure that are used as a write-only Property or are the write portion of a read-write Property.For VBScript code outside of the Class, this type of Class Object Property is usually assignedby a variable or a constant.Property SetThe Property Set procedure is exclusively used when the Class Object needs to storeProperties that are object-based instead of numeric, date, boolean or string subtype variables.Property Set replaces the Property Let procedure. While Property Set and Property Let arefunctionally similar, there are two key differences:1. With the Property Set procedure, in the VBScript code segment (outside the Class block)you must use the syntaxSet Object1.Property = Object2This is because VBScript does not let you use the assignment operator (=) to assign objectswithout the Set command.2. The Property Set procedure makes it clear that the Property is an object-based PropertyExample:Class FileSpec‘ Define a Class blockPrivate master_filePrivate master_FSOPublic Property Let FileName(strName) ‘ Define a Public Property to assign the file namemaster_file = strNameEnd PropertyPublic Property Get FileName ‘ Define a Public Property to retrieve a file nameFileName = master_fileEnd PropertyPublic Property Set FSO(m_FSO)‘ Define a Public Property for an objectSet master_FSO = m_FSOInduSoft, Ltd. 25
Page 3 and 4: InduSoft Web StudioVBScript Referen
Page 5: InduSoft Web StudioVBScript Referen
Page 8 and 9: VBScript Reference ManualInduSoft W
Page 23: InduSoft Web StudioVBScript Referen
Page 75 and 76:
InduSoft Web StudioVBScript Referen
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255:
show all

VBScript Reference Manual for InduSoft Web Studio - ICP DAS

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?