“String - String()”的版本间的差异

String()

描述

Constructs an instance of the String class. There are multiple versions that construct Strings from different data types (i.e. format them as sequences of characters), including:

-  a constant string of characters, in double quotes (i.e. a char array)
-  a single constant character, in single quotes
-  another instance of the String object
-  a constant integer or long integer
-  a constant integer or long integer, using a specified base
-  an integer or long integer variable
-  an integer or long integer variable, using a specified base
-  a float or double, using a specified decimal palces 

Constructing a String from a number results in a string that contains the ASCII representation of that number. The default is base ten, so

String thisString = String(13);

gives you the String "13". You can use other bases, however. For example,

String thisString = String(13, HEX);

gives you the String "D", which is the hexadecimal representation of the decimal value 13. Or if you prefer binary,

String thisString = String(13, BIN);

gives you the String "1101", which is the binary representation of 13.

语法

String(val) String(val, base) String(val, decimalPlaces)

参数

val: a variable to format as a String - string, char, byte, int, long, unsigned int, unsigned long, float, double base (optional) - the base in which to format an integral value decimalPlaces (only if val is float or double) - the desired decimal places

返回值

an instance of the String class

示例

All of the following are valid declarations for Strings.

String stringOne = "Hello String";                                     // using a constant String
String stringOne =  String('a');                                          // converting a constant char into a String
String stringTwo =  String("This is a string");                 // converting a constant string into a String object
String stringOne =  String(stringTwo + " with more"); // concatenating two strings
String stringOne =  String(13);                                          // using a constant integer
String stringOne =  String(analogRead(0), DEC);          // using an int and a base
String stringOne =  String(45, HEX);                                // using an int and a base (hexadecimal)
String stringOne =  String(255, BIN);                               // using an int and a base (binary)
String stringOne =  String(millis(), DEC);                        // using a long and a base
String stringOne =  String(5.698, 3);                                // using a float and the decimal places