ColdFusion“是”eq“真”；“否”eq“假

Question

为什么会这样呢？

<cfif "yes" eq "true">

Yes equals true.

<cfelse>

Yes does not equal true.

</cfif>

页面输出。"Yes =true。“

Answer 1

克里斯和科沙夫的答案是正确的，ColdFusion转换值。以下是有关ColdFusion数据转换的官方文档。

Conversion between types

Value     As Boolean     As number     As date-time     As string

"Yes"     True           1             Error            "Yes"

"No"      False          0             Error            "No"

True      True           1             Error            "Yes"

False     False          0             Error            "No"

Answer 2

ColdFusion具有动态变量类型，并在运行时执行一些奇怪的转换，字符串可以用作布尔值、日期和数字，而无需强制转换，这既有优点也有缺点。

如果需要进行简单的字符串比较，可以使用内置的compare()函数。

Ben Nadel在这里很好地总结了字符串比较选项-- http://www.bennadel.com/blog/236-ColdFusion-String-Comparison-Compare-vs-Equals-vs-CompareTo-.htm

Answer 3

你必须非常小心地进行真/假比较。它们应该很简单，但有时，根据您编写代码的方式，对TRUE/FALSE的评估可能会有所不同。根据几乎所有的定义，FALSE将始终是按位0(在CF中为No )。TRUE将是按位1，但也是Yes和任何非0数字。因此，42仍然是正确的。和-1仍然为真(特别感谢MS Access是/否数据类型:-p)。

由于FALSE总是为0(或NO或FALSE)，因此检查NOT FALSE或NEQ 0通常比检查TRUE更好。然而，即使这样，您仍然需要小心。确定你想要认为正确的东西，并对其进行全面的评估。ColdFusion有时会对真和假变量进行不同的强制转换。查看以下代码的结果：

(感谢伯特·道森和杰米·杰克逊的querySim脚本。)

<!--- set up the fake query: --->
<cfscript>
/**
 * Accepts a specifically formatted chunk of text, and returns it as a query object.
 * v2 rewrite by Jamie Jackson
 * 
 * @param queryData      Specifically format chunk of text to convert to a query. (Required)
 * @return Returns a query object. 
 * @author Bert Dawson (bert@redbanner.com) 
 * @version 2, December 18, 2007 
 */
function querySim(queryData) {
    var fieldsDelimiter="|";
    var colnamesDelimiter=",";
    var listOfColumns="";
    var tmpQuery="";
    var numLines="";
    var cellValue="";
    var cellValues="";
    var colName="";
    var lineDelimiter=chr(10) & chr(13);
    var lineNum=0;
    var colPosition=0;

    // the first line is the column list, eg "column1,column2,column3"
    listOfColumns = Trim(ListGetAt(queryData, 1, lineDelimiter));

    // create a temporary Query
    tmpQuery = QueryNew(listOfColumns);

    // the number of lines in the queryData
    numLines = ListLen(queryData, lineDelimiter);

    // loop though the queryData starting at the second line
    for(lineNum=2;  lineNum LTE numLines;  lineNum = lineNum + 1) {
        cellValues = ListGetAt(queryData, lineNum, lineDelimiter);

        if (ListLen(cellValues, fieldsDelimiter) IS ListLen(listOfColumns,",")) {
            QueryAddRow(tmpQuery);
            for (colPosition=1; colPosition LTE ListLen(listOfColumns); colPosition = colPosition + 1){
                cellValue = Trim(ListGetAt(cellValues, colPosition, fieldsDelimiter));
                colName   = Trim(ListGetAt(listOfColumns,colPosition));
                QuerySetCell(tmpQuery, colName, cellValue);
            }
        } 
    }
    return( tmpQuery );
}
</cfscript>

<!--- populate the fake query --->    
<cfscript>
fakeQuery = querySim('
testID , isThisTruthy
1 | TRUE
2 | FALSE
3 | YES
4 | NO
5 | 1
6 | 0
7 | -1
8 | 42
');
</cfscript>
<!--- End of the fake query setup --->

<!--- Dump the fakeQuery so we can see what we've got. --->
<cfdump var="#fakeQuery#" label="fakeQueryInfo" />

<!--- 
    Not really necessary since the query is created above. Just included for 
    clarity, as everything above this line can really be ignored if connecting 
    to a real query. 
--->
<cfquery name="truthyCheck" dbtype="query">
    SELECT testID, isThisTruthy
    FROM fakeQuery
</cfquery>

<!--- Begin the truthy statements. --->
<br/><br/>
<strong>cfif isThisTruthy >></strong> 
<!--- 
    This one has an implicit evaluation of TRUE or FALSE that seems to be based on a
    broader (and more accurate) definition of what should be TRUE or FALSE. However,
    it's much less clear in what you're trying to do. 
--->
<br/>
<cfoutput query="truthyCheck">
    #testID#: #isThisTruthy# | <cfif isThisTruthy>True<cfelseif NOT isThisTruthy>False<cfelse>NULL</cfif> <br/>
</cfoutput>
<br/><br/>

<!--- 
    The rest of these appear to actually evaluate down to a bit (using the standard
    1,0,YES,NO,TRUE,FALSE definitions) and then they do an integer comparison. This 
    may not be completely what you're looking for.
--->
<strong>cfif isThisTruthy IS TRUE >></strong>
<br/>
<cfoutput query="truthyCheck">
    #testID#: #isThisTruthy# | <cfif isThisTruthy IS TRUE>True<cfelseif isThisTruthy IS NOT TRUE>False<cfelse>NULL</cfif> 
    <!--- 1 IS 1 IS TRUE, but -1 IS 1 IS FALSE. --->
    <br/>
</cfoutput>
<br/><br/>
<strong>cfif isThisTruthy EQ 1 >></strong>
<br/>
<cfoutput query="truthyCheck">
    #testID#: #isThisTruthy# | <cfif isThisTruthy EQ 1>True<cfelseif isThisTruthy NEQ 1>False<cfelse>NULL</cfif> 
    <!--- 1 EQ 1 IS TRUE, but -1 EQ 1 IS FALSE. --->
    <br/>
</cfoutput>
<br/><br/>
<strong>cfif isThisTruthy NEQ 0 >></strong>
<br/>
<cfoutput query="truthyCheck">
    #testID#: #isThisTruthy# | <cfif isThisTruthy NEQ 0>True<cfelseif isThisTruthy EQ 0>False<cfelse>NULL</cfif> 
    <!--- 1 NEQ 0 and -1 NEQ 0 both evaluate to the same. --->
    <br/>
</cfoutput>
<br/><br/>
<strong>cfif isThisTruthy NEQ FALSE >></strong>
<br/>
<cfoutput query="truthyCheck">
    #testID#: #isThisTruthy# | <cfif isThisTruthy NEQ FALSE>True<cfelseif isThisTruthy EQ FALSE>False<cfelse>NULL</cfif> 
    <!--- 1 NEQ 0 and -1 NEQ 0 both evaluate to the same. --->
    <br/>
</cfoutput>

你会得到：

cfif isThisTruthy >>

1: TRUE | True

2: FALSE | False

3:是| True

4:否| False

5: 1|真

6: 0| False

7：-1 | True <-技术上正确

8: 42 | True <-技术上正确

cfif isThisTruthy IS TRUE >>

1: TRUE | True

2: FALSE | False

3:是| True

4:否| False

5: 1|真

6: 0| False

7：-1 | False <-技术错误

8: 42 | False <-技术错误

cfif isThisTruthy EQ 1 >>

1: TRUE | True

2: FALSE | False

3:是| True

4:否| False

5: 1|真

6: 0| False

7：-1 | False <-技术错误

8: 42 | False <-技术错误

cfif isThisTruthy NEQ 0 >>

1: TRUE | True

2: FALSE | False

3:是| True

4:否| False

5: 1|真

6: 0| False

7：-1 | True <-技术上正确

8: 42 | True <-技术上正确

cfif isThisTruthy NEQ FALSE >>

1: TRUE | True

2: FALSE | False

3:是| True

4:否| False

5: 1|真

6: 0| False

7：-1 | True <-技术上正确

8: 42 | True <-技术上正确