void setup() {
char like[] = "I like coffee and cake"; // create a string
Serial.begin(9600);
// (1) print the string
Serial.println(like);
// (2) delete part of the string
like[13] = 0;
Serial.println(like);
// (3) substitute a word into the string
like[13] = ' '; // replace the null terminator with a space
like[18] = 't'; // insert the new word
like[19] = 'e';
like[20] = 'a';
like[21] = 0; // terminate the string
Serial.println(like);
}
void loop() {
}
结果
I like coffee and cake
I like coffee
I like coffee and tea
The String class, part of the core as of version 0019, allows you to use and manipulate strings of text in more complex ways than character arrays do. You can concatenate Strings, append to them, search for and replace substrings, and more. It takes more memory than a simple character array, but it is also more useful.
For reference, character arrays are referred to as strings with a small ‘s’, and instances of the String class are referred to as Strings with a capital S. Note that constant strings, specified in “double quotes” are treated as char arrays, not instances of the String class
2
charAt()
Access a particular character of the String.
3
compareTo()
Compares two Strings, testing whether one comes before or after the other, or whether they are equal. The strings are compared character by character, using the ASCII values of the characters. That means, for example, ‘a’ comes before ‘b’ but after ‘A’. Numbers come before letters.
4
concat()
Appends the parameter to a String.
5
c_str()
Converts the contents of a string as a C-style, null-terminated string. Note that this gives direct access to the internal String buffer and should be used with care. In particular, you should never modify the string through the pointer returned. When you modify the String object, or when it is destroyed, any pointer previously returned by c_str() becomes invalid and should not be used any longer.
6
endsWith()
Tests whether or not a String ends with the characters of another String.
7
equals()
Compares two strings for equality. The comparison is case-sensitive, meaning the String “hello” is not equal to the String “HELLO”.
8
equalsIgnoreCase()
Compares two strings for equality. The comparison is not case-sensitive, meaning the String(“hello”) is equal to the String(“HELLO”).
9
getBytes()
Copies the string’s characters to the supplied buffer.
10
indexOf()
Locates a character or String within another String. By default, it searches from the beginning of the String, but can also start from a given index, allowing to locate all instances of the character or String.
11
lastIndexOf()
Locates a character or String within another String. By default, it searches from the end of the String, but can also work backwards from a given index, allowing to locate all instances of the character or String.
12
length()
Returns the length of the String, in characters. (Note that this does not include a trailing null character.)
13
remove()
Modify in place, a string removing chars from the provided index to the end of the string or from the provided index to index plus count.
14
replace()
The String replace() function allows you to replace all instances of a given character with another character. You can also use replace to replace substrings of a string with a different substring.
15
reserve()
The String reserve() function allows you to allocate a buffer in memory for manipulating strings.
16
setCharAt()
Sets a character of the String. Has no effect on indices outside the existing length of the String.
17
startsWith()
Tests whether or not a String starts with the characters of another String.
18
toCharArray()
Copies the string’s characters to the supplied buffer.
19
substring()
Get a substring of a String. The starting index is inclusive (the corresponding character is included in the substring), but the optional ending index is exclusive (the corresponding character is not included in the substring). If the ending index is omitted, the substring continues to the end of the String.
20
toInt()
Converts a valid String to an integer. The input string should start with an integer number. If the string contains non-integer numbers, the function will stop performing the conversion.
21
toFloat()
Converts a valid String to a float. The input string should start with a digit. If the string contains non-digit characters, the function will stop performing the conversion. For example, the strings “123.45”, “123”, and “123fish” are converted to 123.45, 123.00, and 123.00 respectively. Note that “123.456” is approximated with 123.46. Note too that floats have only 6-7 decimal digits of precision and that longer strings might be truncated.
22
toLowerCase()
Get a lower-case version of a String. As of 1.0, toLowerCase() modifies the string in place rather than returning a new.
23
toUpperCase()
Get an upper-case version of a String. As of 1.0, toUpperCase() modifies the string in place rather than returning a new one.
24
trim()
Get a version of the String with any leading and trailing whitespace removed. As of 1.0, trim() modifies the string in place rather than returning a new one.
下一个草图使用一些C字符串函数。
例
void setup() {
char str[] = "This is my string"; // create a string
char out_str[40]; // output from string functions placed here
int num; // general purpose integer
Serial.begin(9600);
// (1) print the string
Serial.println(str);
// (2) get the length of the string (excludes null terminator)
num = strlen(str);
Serial.print("String length is: ");
Serial.println(num);
// (3) get the length of the array (includes null terminator)
num = sizeof(str); // sizeof() is not a C string function
Serial.print("Size of the array: ");
Serial.println(num);
// (4) copy a string
strcpy(out_str, str);
Serial.println(out_str);
// (5) add a string to the end of a string (append)
strcat(out_str, " sketch.");
Serial.println(out_str);
num = strlen(out_str);
Serial.print("String length is: ");
Serial.println(num);
num = sizeof(out_str);
Serial.print("Size of the array out_str[]: ");
Serial.println(num);
}
void loop() {
}
结果
This is my string
String length is: 17
Size of the array: 18
This is my string
This is my string sketch.
String length is: 25
Size of the array out_str[]: 40